I am considering purchasing this HC-300B from eBay ([Link: ebay.com.au]) to do some DriverWorks developement and was wondering what is the highest version of Control4's OS can the unit be updated to and what is the latest version available currently.

The HC-300E-B supports older 1.x releses and latest 2.3 release. The newer HC-300C Supports version 2.x only and has a faster processor, but a single USB port (this is the eBay model listed). Not a real problem because the 2.3 release really speeded up system response times. The HC-300C also has a recovery pin hole to restore the unit back to shipped release. The HC-300's have been replaced by HC-800 and HC-250 (both faster than HC-1000 and HC-300). For driver development a HC-300 will work just fine. Make sure you have Composer Pro software (dealer sign-in) and knowledge to setup a single controller. Also have a interface (remote control) to navigate and test your driver(s).