Getting the WiFi adapter set up is sometimes flaky, but once it is working, it works just fine. Most of the complaints are simply because people can't get it initially connected. There are several ways to overcome that problem.
I can also tell you that it appears that Obihai may be releasing a new, dual-band version at some point. This is based on the latest firmware adding support for 5Ghz WiFi. There's no other information as to product availability.
Do you need it right now? Buy it. Is this just a convenience issue (you can connect your OBi via Ethernet today, but you think it might be handy or less messy to do away with the Ethernet connection)? Wait.