I am looking for opinions on the MFJ-1020C indoor active antenna. If anybody
has used/tested it please comment on its performance/usefulness.

I use one when traveling, and with a portable (in my case Sony 7600G) it works
very well, but I find I need to keep the gain at about the 2 o'clock position
(around what, 6 or 7 on the markings?) before it starts to overload or add too
much noise. Below that, gain falls off drastically, and so the 'gain' function
isn't really all that variable in the real world. But beyond that, I've used it
with it's whip and it's fine, same with wire antennas (but not too long,
otherwise you end up with lots of imaging/ghosting and then you have to pull
the gain way down to remove THOSE, and it's useless again!).
Just keep a fresh battery or hum-free power supply in it to maintain stability.
I'd say it was worth what they're charging for it, though it would be far more
worthy if the gain feature were as useful as advertised.
Linus