"The lubricant is a part of the tape's emulsion, it's not something you can feel or see. The advice not to mix Sony and other brands is a sound one."
No, it isnt, it is simply ignorant FUD that continues to be passed around. It has been a dead issue for almost 3 years now.
I spent a couple of days researching this a month or two back. Sony DID have lubricant problems prior to 1999, when they reformulated their tape to make it more compatible with the rest of the industry (basically only Sony, Fuji, and Matsushita make all the tape stock for all the various brands if I remember right). Even then it only arose if you used Sony (or other single brand) consecutively for a lot of tapes, 10-30, and then switched. This problem comes up even if you mix new Sony tapes with pre-99 (older) Sony tape so in this regard it is NOT brand specific.
It is an old, tired, and much FUD-filled claim that mixing brands of tapes will cause you problems. Just like the FUD that "Sony tape gives a better picture." Ignorant hype that even professionals laugh at. Do your research, and not just from hearsay or colloquial accounts.
Also, the DV enthusiast community is a pathetically small one compared to the general consumer market at large. If there was as much of a problem as the FUD-spreaders make it out to be, the thousands and thousands of people who buy DV cameras and tapes at retail who blissfully and ignorantly use different brands of tapes every day would be having problems in epidemic proportions and the consumer reviewers like CR would be having a field day. Yet... no word of these problems, and the only place you ever heard of this "dangerous" problem was a DV message board, or a forum, or "some guy who knows video", or your local enthusiast, etc.
Tape brand mixing is NOT a problem. Unless you have a lot of pre-2000 era sony tapes that you constantly use, buy the tapes that fit your budget and purpose and mix to your delight. Professional consensus is that if you truly want to spend to get fewer dropouts (the only real measure of picture "quality" since DV is digital and thus the picture will be the same no matter what brand you use) the real difference is between regular and PRO tape (not dvcpro, that is a different format), NOT brands per se.
End of rant. The panasonic's are a good deal, don't fear any FUD about mixing tapes.