Superb tyres, but I couldn't trust one as a front tyre- it never actually did anything bad, it just always felt like it would, a better rider could probably get more out of them but I need something a bit more confidence inspiring.
On the rear though, they're stunningly good, fast as all hell on anything halfway solid and they rise to the dizzying heights of "barely adequate" when it gets wet, which is more than most fast tyres. The 2.35 has a nice big volume without being too heavy and is about as fast as the 2.1 (unless on sticky surfaces like clay, or run very low). And both are decently tough unlike some racier rubber.
Can't see past them for summer use on the rear, myself. They still surprise me with what they'll grip on.