To me Henry has been one of the greatest strikers of the last five years, and will be sorely missed at Arsenal. OK, so their current form shows that they can perform without him, but I personally don't think it will last.
I think it was all politics, and he isn't interested in that - he just wanted to play football, so his only choice was a transfer. And Arsenal let him go too cheap as well - he should have been at least £20 million - certainly more than Darren Bent!