I love my Jag. Bought it used off TB in really nice condition about a year before they were discontinued. I bought it because I don't like the Fender Jazz shape, but love the Fender Jazz sound.
Its sounds great. Its on the aggressive end of Jazz bass sound, which is exactly what I wanted. When you turn on the series switch, it gets a noticeable boost in lows and mids, making it bite even harder. Anyone who complains about Jazz basses sounding scooped would probably like it.
soloing the neck pickup does indeed fake a pretty good P-bass sound.
I don't use the boost only active mode, but its probably pretty ideal as its very transparent in that it doesn't change the sound character very much at all.
It doesn't balance as well as my Yamaha or my Ibanez, but both those basses are also very lightweight. But, it does hang pretty well overall, especially for a normal weight bass.
The neck is really nice.
I've never had major noise problems with the electronics. But even if you get one that does, there are so many good things about the bass in general that its worth spending the time to shield it properly.