There is always Twitter with their constant downtime, but that’s not really my domain anyway so I can’t really speak to that as a professional, only an irritated user. (Of course Twitter does have UI mysteries like the could-it-be-more-poorly-placed, layout-breaking little rotating arrow that pops down while it attempts status updates via AJAX.) But last.fm’s new site design is, while not an entire whale of fail, certainly a curious direction. From the 90’s grunge look-and-feel to the IA’s seemingly- random emphases. Is the site about my tastes or about discovery? And if at all the former, why are my weekly charts (really the only thing I go to the site for) now an extra two clicks away? And if this is really a music site for audiophiles and not solely for the purpose of marketing music, why the new emphasis on the band pics? The old layout that had a small grid of pics next to (or above) the text list was one of the more ingenious bits of UI I’d come across in the last 5 years.
There is also some terrible new UI copy writing on the site. “Do you want to make friends?” “Make friends?” Really?
There are also some basic address-bar things that could have so easily been made to work better. A basic GET parameter indicating where to send me after I login could be last.fm/login/friendrequests or at worst last.fm/login?page=friendrequests. Instead it is last.fm/login?s=1&backto=http%3A%2F%2Fwww.last.fm%2Finbox%2Ffriendrequests.
Anyway, if you want to find out exactly how much negative user feedback there has been to the new last.fm design, just do some cursory searches or go to their blog.
FWIW, my take-home is, if you have a LOT right already, don’t mess with it. You need to re-emphasize certain areas of the site for the purpose of new “features” (read: ways to make money off this thing)? Then just tweak. Highlight. Iterate. Complete redesigns are so 90’s…just like last.fm’s new one.