Brian,
I'm pretty new - so I defer to the seasoned vets. But, here are my thoughts:
I really like my Rock Box Blue (
http://www.rockboxsailing.com/). I can't say with 100% certainty that it's class legal, but I assume that it is, since you can disable VMG, etc., as per class rules. The non-class-legal features come in handy if you're racing non-class/handicap, as well as for simply learning to sail faster while not racing.
It would be interesting to know if there are strong preferences among other units, like Velocitek ProStart based on functionality, as opposed to personal preference, brand, aesthetics, etc. Seems like the basic functionality is available in several units on the market.
As for the Rockbox, I really like the large screen, the display that works with polarized sunglass lenses (no splotchy black marks), and the versatility of different screen configurations. Also, there are constant firmware updates available, which either add new functionality (based on customer feedback), or improve existing functionality. I'm a bit of a geek - I really like that the RockBox is based on a development platform and that it's constantly being improved.
Keep in mind that all of these units are GPS-based. I would be interested in knowing what some of the more seasoned vets think about replacement of a magnetic compass. I still see a need for a real compass, if for no other reason than, when you're at the start, and you have your electronics set to "race start" mode, you likely won't have enough room on your display for all of the necessary info, including speed, heading, count-down, etc. Better to put speed/countdown on the electronics, and have your compass handy for (real) heading.
On a side note, I am not convinced that the Velocitek Speedpuck actually works according to claims (in particular, the Doppler-shift speed measurements). Any thoughts/comments?
Kuy