In the meantime, one big dilemma I've been facing is whether I should be using float or int for all of my coordinates. More details can be found on my gamdev.net forum post. Ultimately, it sounds like float is the way to go, which means I'll need to do some serious reworking of the engine to eliminate all traces of int from the code. It's going to be a pain, but I think the long term benefits will be worth it.
In the meantime, stay tuned for updates on my Shmup01-based game!