I think when I installed Dropbox I was able to choose the folder, or it created a shortcut on my desktop. In truth the issue was not so much the location, but the internal structure that seemed obscure at the time (this was when GDrive first came out, might be different now).
Dropbox just appeared as a simple, normal folder. That's it. I put stuff in, it got synced. I clicked on stuff inside, and it opened like a normal file in any other folder. It just worked.
I'm pretty sure as skyhook_mockups described it's just a normal folder. GDrive is going to offer a lot once more applications start offering their services services based on what you store in GDrive which is what I see as the differentiating factor for things stored in GDrive. I imagine Dropbox will mimic it in time, but they're behind at the moment.
Dropbox just appeared as a simple, normal folder. That's it. I put stuff in, it got synced. I clicked on stuff inside, and it opened like a normal file in any other folder. It just worked.