I've been using heart rate monitors for years when working out. Until purchasing the Mio ALPHA almost 6 months ago, a chest strap was always part of the solution. The problem was that the chest strap - regardless of the brand / model (various Timex and Polar and perhaps other) would always give out within 6 months or less. This was not a case of the battery needing replacement, as I'd typically have to change the battery more often than that. The strap was, I think, basically killed by my profuse and corrosive sweat :)
Aside from the hassle of having to replace the straps, I hated wearing the chest strap on long runs (which is when I most wanted the heart monitor to function). I'd constantly have to be adjusting the strap, and sometimes they seemed to just get too soaked or otherwise decide to stop transmitting to the watch.
Then my geek buddy Stephen Wissel told me about the Mio. Stephen (a German in Singapore) rides his bike. A LOT! And he'd been using a MIO for a while. This device has been glorious for me. It requires no chest strap, instead magically detecting one's pulse using LEDs and an "electro-optical cell". OK, I don't really understand how it works, but I find it very comfortable, I no longer hassle with chest straps, the watch is easy to recharge (every couple of weeks for me, although I could probably let it go longer between charges), and for my monthly half marathon races, it has performed flawlessly.
My only complaint is that when I'm doing weight-lifting or HIIT workouts, it doesn't seem able to keep detecting my pulse. I think there's too much wrist movement. Experimentation with location and snugness of the watch has still not yielded the desired results. But that's OK. I mainly use the watch to let me know when I need to slow down a little in order to make through a long run without running out of gas!
At the end of each workout, I can review the duration of the workout, the average heartrate, and the amount of time during which I was exercising within my desired range. I then enter those stats into a spreadsheet where I track my workouts. Yeah ...kinda geeky.