I think is has all the layer interaction wossas- hard light, overlay, multiply etc- that Photoshop does, but they're... strange. Multiply makes the layer below darker, for some bizarre reason, instead of how I remember Photoshop's multiply...
So it COULD work, but I dunno either. I'm useless at these things.
Admittedly I haven't gotten around to using either GIMP or Photoshop enough to know what Egophiliac is talking about, but SpindleWinter, you may want to look at the following package for beefing up GIMP for digital painting purposes.
Photoshop calls those blending modes; layer styles are something different (drop shadow, bevel/emboss, stroke, etc.). From what I can tell, they're not part of GIMP but you can get them as a plugin (called Layer Effects). I don't know if they work the same though.