So near, but
After having a Psion back in the day, I'd kept an eye on Planet when they announced the Gemini, but didn't jump in shall we say and finally bought a Gemini off eBay last year to see what I'd been missing. Both the hands on and some of the comments are spot on, the Gemini and the Communicator are both well built though niche products, but both are let down somewhat by software support from Planet.
Judging by the tales of woe from the various online groups, it seems that some of the functions that didn't work on the Gemini, external display support in Linux for one, still has problems if it works at all, on the Cosmo, with most fingers pointing at adoption/implementation of the Meditek processor. What also seems to have happened is software development on the older device tailing off when the newer device arrived. I fully expect that will reoccur when the Astro Slide appears.
It's a pity as they're a nice device, but as with other companies, Planet appear to be funding development of a new product before and at the expense of getting the old one to work as advertised. There again, Microsoft managed that for years....