Mate, it's 90% shock humour. I can appreciate shock humour, in fact much of me and my mates at uni's humour is based on extreme crossing of lines, but Tosh just doesn't do it for me. He's got no subtext, and he looks proper smarmy, as if to say "Can ya believe I just said that!? Can ya!?" – yes, I can, heard it a thousand times before.
He's not doing anything new, and okay yeah his timing isn't bad, but his material is stale and his physical act and delivery is pure by-the-numbers.
Maybe I'm just hard to please when it comes to stand-up, I don't know. I'm a Stewart Lee fan, so maybe that says it all for better or worse, and the only other stand-up act I've seen lately that's really hit a note with me was Zach Galifianakis' "Live at the Purple Onion".