Hi. I must say that the 135i looks great and has excellent numbers. But I would suggest that if you can stomach the extra cash you go the way I went and get yourself a Z4MC.
Sure, on a straight line it won't beat the new M3 but for the money it's the best sporty car BMW makes and you're going to be hard pressed to find a better deal elsewhere.
I do like the idea of the 135i convertible though.
Cheers.