Yeah, I had first gotten a USB N Wireless adapter by linksys and had horrible ping rates and D/U raes were pretty low as well. Couldnt even get youtube to stream anything more than 360p.
If your going to use a wireless solution for a desktop then make sure you something that will suffice. I didnt have much choice so I have a D-Link (unfavorable brand) Wireless N PCI adapter however ping and D/U rates are very acceptable now. I have a 3.6MB/s down peak and it can be more if you use a 5.0ghz band.
There are pcie models as well but they tend to be x1, so there usually low profile.