The Garmin Forerunner 305 is working great for me. Definitely get the bike cadence kit with it, all the information it shoots out at me keeps me working during my indoor trainer rides!
A recent review in Runnersworld sounded like both Polar and Suunto are better when it comes to analyzing the heart beat patterns whereas Garmin's strength is more in the GPS technology. While that might be, the heart rate function in the 305 is sufficient for me...