Doesn't seem any faster to me than LR 4, and seems to have problems whenever you deal with changing a lot of data, for example keywording or geotagging hundreds of images at a time. I never had that issue with LR 4.
There also seems to be a bug when you select to publish a lot of galleries at the same time. My i7 930 CPU sometimes goes to 100% utilization and images publish much slower than if I'd publish a single gallery at a time (didn't think that was the case, but did some testing on the weekend).
I'm also thinking that LR 5 has some sort of major resource leak, because it slows down to a crawl if I let it run (e.g. publishing galleries) overnight then get back to editing in the morning. Closing it and restarting seems to restore performance.
For general editing that isn't moving a ton of data (including adjustment brushes) I haven't had any problems. However the new (semi-useless) Spot Removal Brush is unacceptably laggy for me.