We've actually discussed this at great length in the past. It is a useless stat and we've had a desire to make it not useless. We haven't acted upon it up to this point (last serious discussion on it was over 8 months ago), but the facts are these:
1) Int Casters already never fizzle due to AA's
2) +25 to a casting skill is currently not enough to avoid all fizzling
The best thought we had to make those actually useful was:
1) Make it so +25 IS enough to avoid all fizzling
2) Re-itemize + caster skills for Int and Wis casters
3) Replace the no Fizzle AA with something else worth 21 AA's total that scales.
As is quite obvious, it would be quite alot of work to implement that, with little to no change in overall gameplay if done right. So atm, there is little use in the +casting skills for int casters, and probably won't be for awhile.