PS3 is flakey. I have a slim model now, but i also had one of the launch PS3s until it yellow lighted on me. Previously i was getting great speeds but now not so much.
Previous setup had great speed running on a wireless Linksys WRT54G
Solid almost 6mbs down connection. which is what i was paying for at the time.
Eventually I went to a Trendnet TEW-652BRP N draft 2, and my wifi speeds were terribad.
So i set up a client bridge using the WRT54G and voila my speeds were 10x faster than using the PS3 wireless connection, even though it was still wireless, having the PS3 plugged into a secondary router using it as a wifi adapter seriously took it from about 0.5mbps to 5mbps. You may wonder why i did it this way, well not only did i plug the PS3 in wired, i also plugged my xbox 360 and Panasonic Viera Cast TV all to the secondary router while the primary router was in the office connected to the desktop and a network share(HDD). No need to buy the $80 M$ wifi adapter for the xbox360.
Since then i upgraded to a 16mbps/7mbps service and relocated the primary router to the living room since most of the activity happens there, and decided to just use a wireless N adapter on my desktop. I also upgraded to a Cisco/Linksys E3000.
However my PS3 is only getting 2.7mbps down on average wired, even though my PCs are getting 11-15 mbps wireless. Oddly the PS3 is getting consistent 4.3 Mbps up and occasionally can hit 8Mbps down. Still a far cry from the low end 11 that my wireless PCs get.
edit. HA! Just ran another speed test using the Internet Connection Test in the XMB
19.3 Mbps down
2.2 Mbps up
I didn't change a thing.
Maybe the PS3 connection test software is just whack.