i've done a little bit of research into GPS sport watches, and the garmin forerunner, the suunto ambit, motorola's motoactv, and the nike+ sportwatch seemed to be the finalists for my services. however, the ambit was priced out of my range (a hefty $550), the forerunner is also expensive but no great shakes to look at, and i was already comfortable with nike's getup - that way i can keep adding on to my runs stored on nike+ - so my choice was made fairly simple.
speaking of which, the watch is wonderfully simple to setup and use, which is ideal for when you're beating out tough miles on the trails. one simply doesn't have the time or brain function to scroll thru complex screens and options when you're climbing a brutal ascent, so the big numbers and programmable screen data are ideal.
the setup is so: download the nike+ connect software to your mac or PC, then it will instruct you to plug in the watch - either directly via the clever USB hinge built into the clasp, or by the handy USB cord they include - and voila! the watch starts to charge and you have the ability to tailor your watch's readout (one can adjust what info appears, such as pace, average pace, time elapsed, distance, lap time and/or calories burned) as necessary.
when you decide to take the watch out for a spin, you have the option of linking to the GPS or to the nike+ sensor (for those who are wearing nike+ kicks) as backup, then you can be on your merry way. i've read reports that it's taken some people up to a minute for the GPS to acquire its coordinates, but on my short run wednesday night, it took no more than 3 seconds.
note: nike suggests that you sync the watch to your computer right before stepping outside for each run, in order to locate the latest GPS coordinates. that way, it will acquire your location that much more quickly.
once you've completed your run, connect your watch to your computer and all of the run data will instantly appear, including pace, elevation, lap time (you can set to whatever distance you wish - mine happens to be each mile), etc. in addition, you have the option to link nike+ to your facebook or twitter account, to share with the world your latest running exploits!
update - i took the watch out for its 1st trail run thursday morning at westridge, and it worked like a charm. GPS satellite was linked in a mere 3-4 seconds, and i was ready to go. initially i was concerned about the size of the watch - i'm not a watch wearer by any means, and GPS watches are inherently cumbersome due to the technology behind them - but once it's secure on your wrist, you actually don't feel it while you're running.