personally i haven't had the lag problem before
and that xterm error used to appear but i reflashed and the problem was solved
i have figured that the problem was from some kind of ohmed tweak

and the most noticeable improvements with speedpatch are : much better multitasking, transmission app doesn't f*ck up all of the phone, asphalt 5 doesn't need to be launched twice so it can turn smooth, and the nokia panorama app just doesn't lag any more

hope this helps