Thank you so much for all your interesting replies, I guess I've been worrying about it too much, and although I haven't made up my mind yet, I'm feeling more inclined towards a backpack... anyway, I'll be staying in hostels most of the time and a suitcase wouldn't fit too much in there... by the way, your links were very interesting, Suzanne!
Thanks a lot for helping me and sorry for the late reply.
Hi! This might be a little late, looking at the other dates, but oh well!
I was in Eastern Europe for a month last summer. We stayed in the same city for all of it, with one move in the middle, but we did have to get our bags first to Heathrow from various parts of the UK, then from Bucharest to the city we stayed in on the train, and back to Bucharest on a minibus, including an evening lugging our stuff round Bucharest!
I was the only one of us to take a ruacksack; the others all had suitcases. Although I ended up with really sore shoulders and hips from carrying it (it was a little on the heavy side!), I had no problems getting up and down stairs and escalators, there was no risk of dropping it down the stairs like one girl did with her suitcase, and they all got sore hands from pulling their suitcases.
The big disadvantage I had was when we were stood around, they could all put their suitcases in the middle of us where they could see them - I couldn´t keep taking my bag off to do this, anmd so either had to be the one at risk of someone pick pocketing my bag etc, or stand facing outwards, therefore being antisocial
I think that if you get a backpack that is fitted to your specific body shape and size, then you should be able to carry one around. Unless you are doing heaps of walking, it is mostly just carrying it between transport and accommodation anyway. I don't like the idea of wheeling a bag around - adds to the risk of it being stolen.
You can actually get a travel pack that opens like a suit case and that has the benefit of a detatchable day pack as well.
This response is probably too late to be of use! Just joined the forum for the first time!