I've come to the conclusion that the Intersil Prism chipset is only good for the purposes it was originally manufactured for. That is a simple wireless client and maybe a very basic wireless access point. Use it for anything else and it 'might' work but generally it won't.
But even then it has its issues as I have discovered. When used within a Mikrotik RouterOS system it has issues with connecting to Access Points with WEP enabled. For example I attempted to connect to a Netgear DSL modem/router/AP and it would work fine for about 10min and then just stop responding even tho it is still associated. I managed to overcome this issue by using a seperate Senao Access Point, even then it didn't work 100% as it didn't want to talk to its wireless client neighbours, only the AP and the router behind it.
For now on I will be using CM9's and SR5/9 miniPCI cards, which are all Atheros based.
I wish there were more wireless chipset vendors that catered for this particular market - but I guess we can't have everything and consolidation was bound to occur.