After mine having issues last week but then working solid, it started acting erratically again this morning. The difference I think was that I am working from home and had my IBM work laptop near by and plugged into a monitor next to my iMac. Wireless is turned off on that laptop though. My phone and iPad were somewhat close by. Reboots didnt help, until finally I moved my cellphone and iPad far away from the imac (which is odd because I sync my ipad to the iMac normally without issue), put my work machine to sleep, and then put the iMac to sleep and woke it back up again, and now finally the trackpad is working again.
This thing is susceptible to some sort of interference by I dont know what yet.
Apple emailed me last week asking for information on my configuration and logs based on what they read here in the forum and I sent it off, but havent heard back yet.