The engine in the 335i and 135i is a belter... IIRC there are tuning packages which unlock 400bhp without too much hassle, cooler change, full exhaust, filter and a custom remap.
Plus, the 135i comes with some tasty looking brakes (6-pots?) as standard and I'm sure I read somewhere that its got a more lively diff in it over the 3-series which allows a bit more sideways action than other new Bimmas.
Cheers,
Grant