We are a smaller hospital that have had 3 different flavers of wifi phones. Spectralink i640 then Motorolla, now spectralink 8440 and their pivot models. We have had wireless issues, with coverage, call quality. but it was never an issue related to security. We are using WPA2. And in the Controller we have user rules, that the phones can only access SIP ports. Except for the android phones(pivot), we opened http and a few ports like that.
Our wireless issues were finally fixed after we worked closer with our partner (DataVizion), who came in and cleaned out out profiles, and used best practice docs from Aruba and spectralink, and some of their own past experience.