Its a few minutes work for anyone, just download Imprec and give it a try... Before you comment something you need to try it.
Also what makes you think that will lag or bug?. Once unpacked you can remove unused sections with LordPE. And regarding bugs... i dont know from where you got that info. If all packers produced bugs when unpacking nobody would be using them isnt?. =P
Technically speaking if your patch its applied on runtime then it have more chances to produce bug and will use more time than just executing unpacked main.exe.
Cheers.