well the above-head storage bins are pretty small.  No matter how light you pack, even if you are bringing only 2 changes of clothes its probably going to be a tight fit.  Don’t forget about bringing a towel and several extra pairs of socks & undies.  Waiting for your luggage to come out only takes you about an extra 15 mins, so unless you are taking a lot of flights its not going to save you much time. 
 
having a light load is very handy while in transit between destinations, but I seriously doubt it will be light and comfy enough that you will want to go sight-seeing with it.  If you show up early at the hostel, usually they will be able to accomodate your backpack; either a luggage room, or some will be nice enough to hold it behind the front desk for a couple hours. 
 
 
Packing light definately has its advantages, but I don’t see many worthwhile reasons to avoid checking luggage. 

If you’re going to be buying a lot of stuff on arrival, I don’t see the point to packing light initially. As has been said, it only takes a bit of extra time to pick up checked bags. You can usually ditch your bags at hostels, even if you’re not checked in or also most train stations have luggage lockers for a euro or two. That said, only take what you need – if you can get that down to a bag that will fit in the overhead bins, power to you.

I ALWAYS bring only a carry-on size bag (and yes I am a girl).  The longest I have travel with the bag is 6 wks.
 
I can fit more than a weeks worth of clothes in my bag.  I don’t like risking delay luggage at the beginning of my trip, I do check it on trips home (though not if I have tight connection) because I usually have a lot more things to bring back.  And of course the carry-on size is smaller on inter-europe flights, so I checked it for those flights.
 
Even for shorter trips, I use the same bag.  Everytime I pack it, I think it’s GIGANTIC and won’t fit into the overhead bin.  But once I get to the airport, and see all those business traveller with then “carry on size” rolling bags, I realize my bag is TINY compare to theirs. 
 
For toiletries etc, I bring small sample size products that fit in the allowable ziploc bag.

I definitely believe its doable with just a carry on size bag.  On my first trip I brought a huge back pack that I didn’t take half the stuff I brought out of.  I’m sure the friend I was traveling with got tired of me wanting to mail everything home.  During the last week of my trip I left my main bag in a hostel (at this point not carry if everything was stolen) and just brought the essentials in a small day bag. 

I used to try to do carry-on only, but I gave up the effort once and for all once the liquid ban came into effect. I have a small carry-on tote with one change of clothes and my reading material, and otherwise check one piece of luggage.

Oh wow, I forgot about that liquid crap! What exactly is banned? Everything? I won’t need to check my bag (didn’t last time either) but I’d also hate to have to go searching for shaving cream and mouthwash once I land!

I highly recommend you check the TSA and your airline’s web pages to see the latest list of prohibited items.  The list always seems to change, and sometimes it varies depending on from where you are flying in/out of.
 
 

my last trip i only took a carry on back back and my day pack
2 week trip.  3 shirts, 2 shorts, 1 pants, 4 underwear and socks were packed.  i totally recommend not checking luggage if avoidable.  you can bring small amounts of toiletries and buy if needed in Europe. Happy travels.

yeah no liquids or gels.  and no nail clippers either

At the time of my August trip, the liquids ban had just gone into full effect. There was also confusion at that time about whether even a tiny carry-on would be allowed – for a few days even books were banned in some instances.

Now there are rules about 3 oz. toiletries in a clear 1-quart plastic bag if you want to carry them on, but I can’t be bothered. I’m not sure this applies everywhere you might travel either. Best to check the airport home pages.

What about shaving razors? I brought em last time no problem…

Safety razors are fine. All liquids and gels have to be 3oz or less and you can only bring what can comfortably fit into a 1quart ziplock bag. You then have to take out the little ziplock bag and run it through the x-ray by itself. 

Haha, damn terrorists. Next thing you know you wont even be able to bring luggage with you at all.[8D]

I haven’t checked my backpack in years and years.  I always pack light and put the pack in the overhead bin, or if I’m desperate, it will indeed fit under the seat in front of me.
United once lost my bag on a domestic flight, and it was horrible.
Another friend had his bag lost on the way to Italy, and it really messed up his trip. I simply hate checking my pack, especially on the way out. 
HOWEVER
My last trip ended shortly before the new liquids ban, and it certainly looks like a pain in the butt to deal with that regulation. I agree that checking with the TSA and individual airline is the way to go.

FYI- any liquids/gels needed for medical reasons (i.e. contact solution) can go over 3oz.  US Airways says that it needs to be a “reasonable amount” based on the length of the trip and it does not have to be in the ziploc bag.  However, you need to present it to the security guard at check-point. 
 
I’m also trying to figure out how I can take my pack as a carry-on. 

Great to hear different opinions on this subject. As for myself, I just bought a new pack. I will be checking it in, but it’s not much bigger than carry-on size. (I’m not sure exactly, I haven’t measured it). I decided that with all the items that are banned from carry-ons and you never know when they may change the rules, I might as well check it in, but I am just as determined to pack real light.

Testing for display.

When I go, I think that I am going to carryon my pack, but check a seperate package with all of the stuff that they won’t let me check – 6oz shampoo bottle, knife, and any other random liquids/gels that I have that I possibly want to have for my trip. That way I will have everything for my trip safely in my posession, and should the extra thing get lost, no big deal. They either deliver it to the Hostel for the 3-4 days I’ll be staying there or I just buy a new knife and liquid stuff. I am looking to squeeze into a 35L backpack for my summer trip, and that should do the trick.

Brian

The rule about medical liquids is in fact a TSA rule, consequently it applies the same way to anyone who departs from any US airport. TSA can’t care less whether you go domestically or internationally, for a day of for a year. In fact, as a contact lens wearer I sometimes go with two bags: one for contacts and lens solution, and another one for everything else. I just say “it’s medical” and they never ask any further questions.

TSA 3-1-1 RULE

BUT if your have to clear security in any airport outside the US this exemption may or may not apply, so it’s best to check specific airport’s or aviation authority’s website.