Personally for me a device would need to have a magnetic compass so that rules out the Speedpuck.
I like the Novasail line of products since they have both and are still affordable.

Since most of the GPS devices are highly programmable what do you think would be a maximum set of features?
For me tracking, speed, and heading would be about it.
Not sure if distance-to-line, VMG, preprogrammed marks/gates and a good idea.

Same goes for the smartphone apps where the possibilities are basically endless (have phones on the water exchange data with each other etc).