the main thing I've been thinking about when I started getting interested in 15mm (but it was the same with other scales too) has been to find good rules to play with.
I appreciate systems in which every mini has his own opportunity to be the hero of the game and all miniatures are based individually. Said that, I found the best resources are on the web.
I'm a fan of Ed's Two Hour Wargames rulesets (http://www.angelfire.com/az3/twohourwargames/index.html ), that are completely different from any system I had the opportunity to to try: in Ed's games every action your mini do corresponds to a reaction from the other side... and the result is really an "alive" table!
I playtested a bit Chain Reaction 3, free on THW website, and found it very versatile. I'm planning a battle with some friends using the the scenario proposed at the end of the rulebook... another innovative aspect is that you can also play same side!
About miniatures, the battle proposed as sample from CR3 is "regular troopers vs insurgents"... my Light Recon squads look forward to act as regulars... while I already ordered -with some help from my very patient girlfriend- the fantastic Sahadeen warriors from Rebel Minis (http://www.rebelminis.com/sahadeenarmy.html ) to take the role of insurgents!
I'll update about the project and post pics asap!