Little more on the expensive side but I've had such great experience over the years with Tumi that I'm reluctant to use or recommend any other brand. They are sturdy and well designed, both on the outside (they'll fit in the overhead bins) as well as the inside (maximum use of the space), but they are really easy to carry around. Some models start out a little on the heavy side, so if you want to be sure, read the reviews for particular models carefully.
I have never regretted, after years of buying cheap luggage, that I finally plunked down some real cash and invested in Hideo Wakamatsu luggage. Their small wheelie has the best wheels and most durable handle of any luggage I've ever owned, and I can be really hard on my baggage. The best part of this brand is that the luggage doesn't add a lot of extra weight.And they are well designed to provide maximum space without compromising strength. I will stick with this brand in all my future luggage needs.
I think the trick with traveling, whether it be international or just barely out of town, is to pack light. I went to Tokyo for 2 weeks with a single carry-on luggage bag (the kind that you can wheel behind you). I didn't have to deal with checking bags or lugging some heavy luggage around. I didn't always pack light, and I learned my lesson the hard way. Learn how to pack light here: http://www.onebag.com/list.html or http://www.reidsguides.com/t_pa/t_pa_packing_light.html
I second both JessieR's and robbie's brand recomendations (Hideo Wakamatsu and Tumi) for wheeled luggage.
If you're traveling to countries/cities that are not as 'modern,' (E.g., cobblestone streets, packed dirt streets, tons of narrow stairs), the better bet is to find a wheeled carry-on that you can also carry as a backpack because wheeled luggage is great but only if there's something for them to roll on.