You'll be surprised at how naturally curves just kind of pop out of wood once you get the feel for it.
I just bought a Microplane over the weekend, and I have a spokeshave, files, and a rasp as well, so here are my comparative impressions:
I love the spokeshave. I bought a cheaper one (a Stanley, it was $20 or $30) and tuned it up so everything is as sharp and flat as is possible. It works great. I've found that even set to take off as little wood as possible, it's best not to use it to get extremely close to finished dimensions. (At least not at my skill level.) No sawdust is a big plus.
I don't like the rasp much, but maybe it's because I (again) have a cheap one. $8 or something. I just don't see anything it can do that I wouldn't prefer using a file to do instead. It leaves quite a rough surface, and I can't control it as precisely as a file. . No sawdust, though.
I have a singlecut and a doublecut file, and I use them constantly. The neck I'm currently building, I started shaping with a spokeshave, then moved to files and sandpaper. Worked nicely.
I haven't used the Microplane very much yet, but it seems to be somewhere in between a rasp and a file. It's not as coarse as a rasp, but more aggressive than a file. I'd use it instead of a rasp, but I think I still prefer files.