I use the FR 305 with Sporttracks on the PC. Couldn't be much easier. You can get the drivers from Garmin's site (Sporttracks even tells you where to find them.)
I have the Edge 705 now, but I logged thousands of miles on the FR305 last year. The 405 appears to be a bit smaller, which would be nice. I'm not sure what other new features it has over the 305.