Curiosly in the begining I found it laggy and would suck the battery like crazy, but now after a week it's speedy and the battery stabilized. In essence the more I used it the better it got.
I've seen posts where people that transferred the contacts using the transfer option from phone to phone had issues with the performance of the phone as well. In order to sort it if I remember correctly the cache needs to be cleared. To do this the phone needs to be entered in recovery mode and the cache cleared
