Over the years I've had two different routers and two different PS3s and they've all worked fine over wi-fi. This includes streaming HD movies via PS3MS so having media server enabled doesn't change much in my experience.|
I've always used WEP though as opposed to WPA (for one reason or another, I know it's basically a waste of time) so I don't know if that means anything. All I can tell you is that I've only noticed the Store going slowly during massive new releases, and even then that doesn't include actual download speeds which are always, always fast for me. I'm seemingly one of the few who can stream HD movies from the store without a hitch too.
This issue has always completely baffled me because I've never seen it in real life. A friend of mine used to complain about it, turned out the problem lay with his 512kb 'broadband'.
21 consoles, 5 handhelds, 2 PCs, 1 Mac and about 700 games from the past 30 years. Every major manufacturer and developer represented. Still a fanboy for disagreeing with you.