Well, not conclusive testing but here's what I've noted thus far:
Connection is unchanged, stable as ever, up/downstream SNR is holding at previous levels.
Download speed is unchanged, maxing out at around 888k/sec.
As previously posted, the WPA/WPA2 issues are gone and I can now connect any of my devices first time, every time.
I've tried every combo on the router now (except the enterprise radius server options as I don't have one) and they all work a treat. I'm now using WPA2 encryption with a 62-character key.
For some reason 63-character keys cause devices not to connect, they just time out waiting for the router...
The issue where the wireless light fails to flicker when wireless transfers are in progress has been fixed.
All in all, the best update yet (especially from my point of view as being on WEP was really annoying!).