Bipoles and dipoles are essentially the same thing, just that one is wired 180 degrees out of phase.
Bi/dipole vs monopole is really a personal preference. I prefer monopole surrounds for music, and I listen to about 75% music. Of that 75% music, most of it is 2ch, so the surrounds are not used. I hate the artificial sound of most DSPs for music.
Dipoles for fronts? No. Dipoles are designed to give a difuse sound, which is good for surround effects, but not for your main channels. Bipoles would work for fronts, but I don't think it would be worth it. Just get a nice monopole tower and you will be just fine.
Sorry, but I have to disagree Brian, bipoles really do add to the HT experience imo.
Doug, truthfully, you're just going to have to go listen to them. I auditioned a lot of speakers including monopoles and dipoles (Martin Logans) for fronts but I found that I distinctively preferred the bipolar sound because of the tremendous feeling of depth they presented. I use my system nearly exclusively for HT with occasional music listening and I love them for that too but for HT bipoles really added to the experience.
What I'm telling you is what everyone else is going to tell you-- go listen. Your fronts will be the foundation for everything else so just be sure that whatever brand you buy that there's a complimentary center channel to go with it and be sure you're happy with the whole setup. For surrounds some people like dipoles, some like directs, and there are bipoles which are like a combination of both. No matter what, take your favorite music and DVDs and go audition. Spend as much time as you like and when you've narrowed it down to a few then come back and ask specific questions about the models you like. There are lots of terrific speakers to suit every taste so try a bunch.