I decided to go the other way and see if I could train effectively with relatively simple electronics that don't generate a whole lot of data. I got a fairly cheap/simple Polar FT7 HR monitor, a wired Cateye Strada bike computer with cadence, a Kurt Kinetic trainer, and a simple digital watch with stopwatch function. I use the stopwatch and a cue sheet to let me know when to start and stop intervals. I can convert trainer speed to power using Kurt's published power curve/formula. So I predetermine what speed range corresponds to the power range I want to hit in the intervals (that goes on the cue sheet too). I write down just a few data points in a paper log after each session: time of session/ride, distance, ave speed, max speed, ave HR, max HR, calories (which are of dubious accuracy and value).

I decided I would use this system for a year (I'm just a few weeks in now) and see how it goes before deciding to upgrade, and if so, what to upgrades to do. I'll be reading other replies to this thread with interest!