Whats the solution?
Set your wifi router to use G wifi mode. My router was using N mode - This seems to have issues with the Broadcom wifi drivers, once this was changed to G mode my wifi speeds came straight back to normal levels :)
Ubuntu / Broadcom Slow Wifi Issue Solved
Since upgrading from Ubuntu 9.04 on my HP Mini 2140 I've found that all recent Ubuntu derivatives (Jolicloud etc.) and other recent distros (Fedora 14 etc..) have an issue with the Broadcom wifi drivers where download speed goes back to dial-up level. If you search ubuntuforums.org you'll find heaps of posts all complaining of slow wifi speed with Broadcom devices (4322 in the case of my HP Mini). most posts have no real solution.