DX has made making 2D games a very different sport.
I mean, traditionally you'd have to worry about so much more, like scrolling the screen, zdepth - and you'd be stuck with a very limited 2D engine that might not even support alpha. These days, using a 3D engine for your 2D game means you have the benefits, like nice transparencies, AA, particles, rotation - all the stuff that is really difficult in 2D is par the course in 3D engines.
Darkbasic makes making psuedo2D games fun, it is quite easy to knock up a game engine, especially when you can cheat and use a matrix for your level, you can have a retro style tile engine up and running in an evening. I think it's important to know all the techniques, because 2D coding is quite straightforward and predictable - it's not so much something that you need to practice, especially in DB. I mean, load an image and paste it - it's not rocket science, really the tricky parts involving true 2D are GUI's, and they're a logical problem more than anything, like organising and using them effectively is far more complicated than putting them on the screen. The thing is that it's all important learning, if your level editor for your new game is painful to use, then you won't want to use it - spending time on a good set of GUI functions keeps editor development speedy and fun.
Van-B

Put away, those fiery biscuits!