UPDATE 12/30/2011: Couple more rounds under my belt with the unit and I like it even more. It's plenty accurate enough for my ability to hit a yardage target, and it works even when stuffed in my pocket. Takes a few minutes sometimes to lock onto the GPS satellites from a cold boot, but the thing just works, auto detects the course I'm on, detects when I'm on the green and asks if I want to input the score for the hole, and then auto switches to the next hole as I walk to the next tee box. I think about all that could be done to improve it is make it faster, give it a capacitive (instead of resistive "clicky") screen, and make it cheaper...although at almost $100 less than I paid these days, it's looking better and better. Upping review to 5 stars.
ORIGINAL REVIEW: While I think all of these devices are massively overpriced (since you can get faster, larger screen "road" GPS units for about a hundred bucks these days), I did a lot of research before choosing this one (and I was not interested in paying any subscription fees). It really came down to this and the Garmin G5, which I think is also a good device.
The problem I had with the G5 is it's HUGE, like an inch thick at least. It also is not appreciably faster and is more difficult to see in the direct sunlight. Keep in mind no color screen of this type is going to be perfect in direct sun but this one does pretty great if you just tilt it away from yourself slightly. I had no trouble seeing it during a round starting at noon yesterday in very harsh, bright sun. Battery seems great, I've only lost one bar (out of four) during a 4.5 hour (SLOOOooowww) round yesterday, meaning it should be good for at least 2 if not 3 rounds before needing a recharge.
So far on the local course I played, yardages were dead on. A few too many button presses required to use the scoring module, but it does work. The shot distance mark-off works great, but no way to store distances for clubs the way I think the G5 does. The scoring and stats module of the G5 is better I think...but again, that size.
I wore the GolfBuddy World on my belt yesterday using the included clip and it stayed put even when jogging out to an errant shot, and never got in the way. My arm would rub against it occasionally necessitating wiping the screen off periodically since I was wearing sunscreen and the smears made the screen difficult to read.
The support from GolfBuddy seems good so far as well, although I haven't needed to really put them to the test. There are plenty of courses available for me, in all the locations around the world which I travel.
In any case, if you're prepared to pony up this kind of cash for one of these, I think your choices right now are either the Garmin G5 or the GolfBuddy World, and if you're concerned with bulk, definitely choose the World.