The problems with version 5 seem to surface on larger networks. We have several clients with very large production networks, each with several hundred sites, thousands of APs, and multiple multi-node clusters worldwide. We are responsible for managing and maintaining these production networks so we are very cautious with upgrades. We do our own testing and we've not found a single version 5 release that we like. We've kept all client production networks on 3.6.2 with one exception - a single 4-node cluster managing APs and switches that's running 188.8.131.52.496 (the version we dislike the least).
We very much look forward to having a stable and tolerable v5 release one of these days, but because our neck is on the line, we intend to keep the our clients on 3.6.2 until there a there is a release that passes our testing. If you check the Ruckus support site, you'll also find that TAC's recommended version for SZ or vSZ is 184.108.40.206.222.