I'm one of the developers enticed over and I have released apps on their store and have another in the pipeline but they're android apps ported to
.bar files. It's a pain in the arse to do and compounded by the fact that the android environment has been deliberately crippled to prevent users from installing other app stores, or even from sideloading. Apparently RIM intend to disable sideloading altogether but how it affects devs will be interesting to see. Either way it's really annoying.
The OS is pretty good but it has it's share of annoyances. I hate the way the lock / pin screen sometimes rotates and sometimes doesn't depending on the app underneath (i.e. if you have mail open under the lock screen it won't rotate). Some icons like Music / Video mysteriously disappear from time to time. Some of the default apps are a mixed experience mess or point to proprietary commercial services (e.g. Zinio). Sometimes wifi goes awol and a total reboot is required. The browser is fast but lacks options like password manager, edit bookmarks, or to put touch activated placeholders for flash. Lots of little things that add up to be annoying. A .5 release could really nail the experience but I fear it may never happen. If anyone ever figures out how to root these things, I'll be installing ICS like a shot.
I really think they should just dump their OS altogether IMO. RIM's value is in security, certification and business infrastructure. They can provide this as value added software / hardware over Android. I think a security hardened Android would be extremely popular.