CyanogenMod team recently released its stable build of 7.1 release, but it seems things did not turn out to be so much stable for Samsung Galaxy S II users. So, CyanogenMod SGS Team has decided to treat it as a release candidate and the stable release will be rolled out soon.
Some of the issues that users are facing right now with 7.1:
- Constant loss of Cell data connection
- Inconsistent and irregular Bluetooth support.
- Wifi issues with drops and pauses. Mostly fixed with proper WPA supplicant.
- Apps dependent on regular data connection often crash, most likely related to communication between baseband and Android.
- Regular app Force Closes, even after permissions are repaired.
- No WPS support (pin, PBC, etc)
- Camera app crashes
Source | Thanks for the tip Basavaraj

I had all these troubles and to add to it, i was not able to register my google account also in the beginning.