The complaints aren't really about the look and the performance.
Most people complain about a lot of small usability mistakes and some big usability mistakes (like the calendar and music apps). And there's the crashes of course, although they got a lot better with 7.0.4.
Does iOS7 cripple iDevices in general? Difficult to say. On an iPhone it could be too hard a judgement.
On an iPod touch however it certainly does. The new music app is retarded beyond any excuse. Pushing it out as an update to a device that's specialized on music playback is a blatant disregard of usability. I think iOS7 did cripple my iPod because I wouldn't buy the device again for the same money knowing that it runs iOS7. iOS7 (particularly the music app) has devalued my iPod.