I hate the Y cable on the Senn's. That and their spring connectors. If you have them or are considering getting any of the the Senn models that have the spring connectors, expect to have problems at some point with intermittent contact between the spring and the cable end connector. It's a fairly easy fix, but I think it's a poor design. Here's instructions for the fix, courtesy of "jeepy206":
http://www.pbase.com/jeepy206/580_intermittency_repairs
Also, the foam (next to the drivers and in the headband) on my old 545's rotted fairly quickly. That pissed me off, as well.
I do like the sound of a few of the Senn models, though. Too bad I don't think the design or build beyond the driver is quite there.
Pleather pads on AKG's piss me off, too. Glad to see they went with velour on the 701's.