Tri watch VS. running watch+bike computer.

Depends on your needs, but I do fine with a FR15 for runs and the Garmin 520 as a bike computer. (I race only with the latter.) Tri watches are pricey and tend to be bigger than my arm anyway. Particularly if you're not doing OWS, it doesn't provide a lot of interesting additional data to look at that a run Garmin and bike computer wouldn't. Not sure if it takes HR on the swim or not, or if it requires a chest strap for that. I've just never felt the need to have that kind of detail for the swim--I do little OWS in training, in the pool, I know my distance/pace from laps and pace clock, and I have a good sense of pace for racing tri swims. Maybe it would give helpful data for people who tend to start too fast or push too hard on the swim, or do a lot of OWS in training?

The 520 works very well both indoors and out and if you do decide to get a PM in the future, it syncs well with that, as well as a HR monitor. Easy to upload to various logging sites. There are a few quirks, but probably common to most computers--sometimes the power or GPS will cut out if there is electrical interference (from other athletes' tech toys, cars with onboard navigation, beacons near harbors and airports, etc.). Kind of annoying. It also appears to fail if water gets into the contact point where the download/charging cable goes. The only time my 520 has ever failed was at 70.3 Worlds.....Arrrgh! I basically eliminated all possible causes except it getting wet with a leaky water bottle en route to transition. Maybe keep it covered and closed with duct tape or something when racing/riding/ in wet conditions or setting up transition.