On the new Macbook Pros the issue of Bluetooth interfering with WiFi network is really bad. So bad that I could not use my bluetooth mouse while surfing the internet!
The issue is caused by the fact that both bluetooth and most WiFi network use frequencies near 2.4Ghz; signals are then overlapping and disturbing each other. So, some slight interference, is normal and maybe it’s more serious on the rMBP because it has a single card to handle both WiFi and BT.
The solution consists in setting priorities between WiFi and bluetooth (giving WiFi signal an higher one).
You have to launch the Terminal (Applications>Utilities>Terminal), paste the following code, press Enter and insert your admin password.
sudo defaults write /Library/Preferences/com.apple.airport.bt.plist bluetoothCoexMgmt Hybrid
The problem, in facts, is not solved. It can’t be solved, if radio signals are using the same frequencies. But, at least, I am able to use the internet with my mouse (that’s a pretty basic task :D)
The real solution would be to use different frequencies for the WiFi network: to avoid this kind of issues, WiFi is also available in 5Ghz frequencies, however just a few routers support that.
If yours do, all you have to do it to enable it in the settings page.
Please note that 5Ghz WiFi has a shorter range since higher frequencies can’t pass through objects and walls like lower ones do. Some routers even support both frequencies, so your devices can use the 5Ghz when in range, and 2.4Ghz otherwise.
However, if you don’t want to upgrade your router, the command I wrote about earlier is a great trade-off!