I know what you're talking about, seeing people hunched over walkers. From what my RN sister tells me, that's usually caused by one of two things: something wrong with the spine that won't let them stand or (more commonly, I think) poor education on walker use. You need to have the walker properly sized to you and learn to use it properly. Don't get the one with the basket under the seat: it forces you to stand farther back from the handles and your means of support (which causes you to lean). I use the Dolomite Legacy 600 (it's a pretty blue), and when I stand in it, I look like this:
http://www.phc-online.com/v/vs.../images/dol_seat.jpg
I use a four-wheeled walker with the brakes in the handles (kinda like a bicycle hand brake). The basket being positioned in the front is removable, and the seat folds up completely out of the way. In my opinion, it is a much better setup than the under-the-seat basket models. When I use mine, I fit between the handles easily with my elbows only slightly bent. If I straighten my arms, I can bring almost all the weight off my legs and still be safely balanced between the handles. My fibro pain tends to hit worst in my lower back and hips, so the best part is that I have a seat on mine, and a basket in the front, so I can do a little shopping and then
sit down while waiting in line. The ability to sit while waiting has been the greatest benefit of the walker over the cane.
The handles also need to be set so that they aren't too high or too low for you. I actually have to change the position of mine based off the height of the shoes I'm wearing that day: it can make that big a difference in how I feel.
Oh, and a fun little fact that many people don't know: a four-wheeled walker is a blast to use with a pair of heelies -- those sneakers with wheels in the heels. I can cruise through the mall with ease with a pair of those and my walker as stability and external brakes. Just don't get going too fast and hit the brakes, or you'll go
apples-over-teakettle over the front of it. I know this from hilarious experience. I am so glad my husband didn't have his phone out that day, or I'd be a YouTube star. ^_^