Just got the Forerunner 310XT
It is sweet. Very easy to use. Screens are intuitive, display is large & band is made for smaller wrists. I looked at the 305 but decided that I would probably want the 310XT for swimming, so I can count laps.
It came with the softer heart rate monitor band, so it's OK to use in the water. I've only used it on the bike so far. You can program in alarm times - good for somebody like me who forgets to stop & eat during long rides. I haven't even scratched the surface on everything that it does.