If you record onto a CrO2 tape, using the Cr02 setting on that deck, and then play it back in the normal mode, you will hear an abnormal boost of high-end, which may be quite piercing. (or nice, if you want to use that as an auto EQ method for muddy-sounding recordings.)
As is, Cr02 particles move around more when they get high end recorded onto them, so the high end shows up more.
I have yet to hear a Fe02 cassette that didn't give me any noticable high-end dropouts after just 1-pass recording. Cr02 tapes can have the same problem of they're cheaply made. Only high-quality, new, few-pass Cr02 cassettes have given me consistent sound reproduction, in terms of fidelity and lack of dropouts.
Then again, I only use cassettes for my car. My problem was transferring my favorite CD's to cassette. I use a fairly decent RCA tape deck (no noticeable wow and flutter, and easy to adjust the speed.) I tested tape transfers using old maxell Fe02's, new maxell Fe02's, new maxell Cr02's, old sony Fe02's, and various other old tapes of various brands. Only the new Fe02 maxells gave an acceptable reproduction of my CD's.
I'm no expert, I just know what works for me may be different from what works for you. I have a ZZTop album on a standard Fe02 cassette that KICKS ASS. I've played it at least 200 times, and it's still as pure sounding as ever, so I know that Fe02 tapes still have their place. They just don't work for my recording needs.
-callie-