It works quite well on my Camry with a heavy duty Diamond mount. I think most folks that say that it didn't work well for them forgot 1 thing - the antenna must have a good ground (and I confirmed this with an Austin tech some years ago when I got it). My poor old 245 gets nailed with intermod when I'm in the Woodlawn area, but that's the scanner's fault, not the antenna.
You can cut the top whip to improve the VHF lo band sensitivity somewhat. While it's not actually designed to work on the civil air band, it does seem to work fairly well there - I can, at times, copy Potomac a/d (both sides) when I'm near Security Square mall. The one thing I really like about the antenna is that it's sturdy - it survived several nasty snow and ice storms (including the Great Blizzard of a few years ago) with nary a problem.
Until I get my 396 - when I intend to put several milair freqs, and I don't expect the Spectra to work well there, since it's not designed for it - I'm keeping mine.
73s Mike