I've noticed after downloading and installing the new 4.20 update that my wireless download speeds have drastically fallen. Before the update I would get 4.5 mbps at worst, now I am getting 330 kbps. I've even moved the router closer than before the update. My signal strength is at 92%. I have no issues playing online or connecting to PSN but downloading anything from demos to updates takes forever. Recently I downloaded the Battlefield 3 update and it said it would take 755 minutes! Any help with this issue would be appreciated. I would like to avoid a direct connection between my router and PS3 as I don't feel like having ethernet cable running all over the house.
Have you tried rebooting your router? Sometimes switching a router off for a few minutes often helps from experience.
I have similar speeds myself around 5 to 7 MB connection can usually download 1GB of data in 40 to 50 minutes. That's using a wired connection, but if you don't want wires trailing round your house web search homeplugs use them myself upstairs.