My Sony XPERIA Neo MT11 and Android ver 4.0

I am having problems with my cell phone I upgrade my Android Ver 4.0.4 and it has lags a bit at times. I know that Rooting my Cell phone will void the warranty so I decided not to it.1 GHz Qualcomm Snapdragon processor is not powerful enough. :=( . Just like I felt before upgrading).-