same here.. when saving or launching apps and scrolling too.. it seems like an overall experience to me..
When moving to new firmware, general advise is to keep using for 2 to 3 days for the ROM to "settle" down.
In between this period, your battery might seems shorten, system a bit lag or not responsive.
What I do understand when moving across major release (e.g. 4.1.2 to 4.2.2) some other stats may be cleared off such as your battery stats, your dalvik cache and etc and need time to rebuild.
So far after using .423 for weeks, system is pretty stable and responsive. However I encountered some system lag when using down-clock using "No-frills CPU Control", to around 1GHz. Letting the system control the CPU speed this time round seems to be a better idea.