I used webOS for as long as it was reasonable to do so - but CM9 is clearly a better choice for almost anyone. I tweaked and fiddled and played with webOS to get the most seamless experience possible, spending a TON of time on it, and in the end it's just a ton of effort expended to bring the device up to "adequate". Most of the fixes and tweaks etc that I recommended should have been baked into the code for webOS -years- ago. It's really a shame how hard they dropped the ball - and this is coming from someone who's been a webOS convert since I bought my very first pre- on launch day and has put up with all the negatives. SOOOOOO much promise, massive failure to deliver. I can't help but feel like even the open-source effort is a bit slow and stalling, and the timeline on this is doing nothing but sending experienced devs who -were- webOS faithful on to other devices.
As it sits, the touchpad running CM9 is one of the most capable ICS-equipped tablets on the market. It's a beast in terms of CPU, graphics, screen, etc. The newest nightlies run beautifully. I can't see any reason why a TP owner wouldn't want CM9 installed on their touchpad. Even if you still use webOS (I do from time to time), having CM9 on there is a no-brainer. 20 seconds and you've rebooted into CM9 ready to use it's vast array of apps, enjoy a much more capable web browsing experience, and generally massively improve the usefulness of your tablet. There's no downside.
That's why the webOS users are a bit sparse, and that's a trend I only see continuing.