Since this is the replacement Kodak brought out to Kodachrome, most people want to compare the two when analysing this film stock. Against K40, this film stock does have more noticeable grain, and yes it does get overexposed by 2/3 stop in many Super 8 cameras, but it has a lot of appealing qualities that make it well worth buying.
The colours look rich and vibrant with 64T, and I think it might actually fare better under tungsten than Kodachrome - the faster speed of the film makes a noticeable difference in giving you slight more depth of field. One of the great things about 64T is that you can recut the uppermost notch in the cartridge with a stanley knife, and make the camera think it's Ektachrome 160T - then get it pull processed by Nanolab.com.au-, and you've got a low light film stock that looks better than the original Ektachrome 160T did! That's what I'm doing right now with 2 carts I just purchased, and I suggest you consider it too.