Yes. It's a known bug that is being bizarrely ignored. If you have good 4G signal it may not be an issue. But what certainly is an issue is it being sluggish after turning off 4G. If you watch your logcat logs, you can see that there is some sort of WiMax polling activity occurring every 2 seconds, even after turning the radio off.
The only way to stop the polling-even-with-the-radio-off, and regain your performance is turn make sure the radio is set off and reboot the phone. Now, if you're in a 4G area and turn it ON and get good signal, that may 'fix' it as well...