Yeah, it seems to really vary. In my short time of playing around, I haven't noticed much reduction in quality at all around my city (Brisbane, Australia) over Google Maps.
The only thing I noticed so far was that St. Lucia Golf Course was incorrectly labelled as Indooroopilly Golf Course (which is a few kilometres away). I reported it.
I'm actually fairly impressed with the number of businesses from Yelp - I wasn't aware that it was available in Australia, but it has all of even the most obscure little cafes and shops I've searched for around town.
Their place data needs a lot of help. e.g. If you look for the nearest hospital from me it will take you to a new retirement community built on the site of an old hospital. It is easy to report the problem, now to see how long until it is fixed.