You definitely should consider not using NTFS on older or slower machines if you intend to play games etc, as you *may* well get a performance drop. But on anything with a good hard drive at 7200rpm or faster, you may actually get a very slight performance increase due to the fact NTFS fragments less than FAT.
Of course it varies from machine, i dont actually notice any performance increase on my NTFS drives...but i do notice that they get dont "sluggish" as quick as my old FAT drives used to, due to them fragmenting less...