Many (all that you described and more) changes between the first year AI (2008) and the latest (2012). The 2008 was a great boat, but by the 2012 model Hobie has fixed most issues than some people have encountered.
A 2008-2010 in good shape is probably worth between $2000-$2600us used, depending on any upgrades (some were free) and additions included (carts, sprayskirt, etc.)
Good luck deciding, but go for it (which ever you decide).
- - - - - Hobie Island Sailing since 2006 - - - - - 2011 & 2015 Hobie AIs and a 2012 TI