I was experiencing super slow internet on my macbook pro for some time. Whether I was in the office or at home it was slow. But the puzzling part was that some parts of the day it was fast and sometimes slow on the same WiFi spots. And it was fast for others on their PCs or Macs.
For sometime I lived in denial that my shiny new Macbook Pro could be at fault here. But when it became intolerable I thought of giving it a chance of Googling to find out if others were experiencing the same. Very obviously, it was a common problem.
When I tried to look for a solution, I figured that the slow internet was a result of some pre-determined DNS setting in my macbook.
In Mac OSX Lion, these are present under System Preferences > Network > Select Wifi on the left column > Advance > DNS
Mentioned above are the changed values. But there were some fixed random values here when I opened this. I am not sure where those had come from since I never set it myself. May be it was somebody from the IT department of the company that I once worked in for 2 months.
You just need to change the DNS values here (you can use the ones shown, they are from OpenDNS). Add them if nothing is present here. You can also use OpenDNS servers. Here are complete instructions on how to change these and what to change them to:
How to change DNS settings to point to OpenDNS servers
After I changed the DNS settings, my internet is running as fast as Leopard (perhaps that was a better name for the OS, not Lion).