On a macro scale the iS101 and iS105 look very similar.
On a more detailed scale, the new iS101 has a wider (but thinner cross section) , more efficent tail now featuring mini wingers for better release and fin drive and subtly but importantly the overall scoop and rocker profile have been refined.
The overall volume of the new board remains basicaly the same (or a couple of Lt less than 105, depends on whose figures/measurements you consider).
Upper wind limits and in jibes the new board adds a bit more control (bite/grip on the water) , and the overall efficency increase of the planing area and release from wingers gives higher top speed potential than 105(same also on 111/122/133), and similar potentail speed benefit in less than max conditions also.
Obviously, the new 2007 iSonics are a logical "second generation" refinement from the initial 2006 versions (iS105 etc)- not quantum changes, but still noticeable.
Add in a range of the usual "progressive" details like upgraded straps (SlickStrapII), new 2007 fins, new laminate spec, Technora replacing Dyneema etc, tighter control on rocker profile etc. DockLocks lock insert.
Hey, you even get red paint on the tail cuts - it has to be faster
Cheers ~ Ian