I've always heard you are supposed to stick with one brand of tape because some use a wet lube and some a dry lube. That being said I mix em' up all the time and have not had any problems (knock on wood). Also the cheap stuff has worked as well as the spendy stuff for me.
Great, I just ordered 25tapes from that place that jay suggested. and I'm waiting for them to come in. I ordered consumer tapes, but it came with a master tape, so I want to make sure that I can use both tape types.
Dave, I did this with my XL1s, used both grades, and I didn't have any problems. With the XL2, I've used one grade of tape (just to keep things simple).