I was in the market for an ABG while ago, and I happened upon one in Athens, GA at a store called Chick Music.
I kind of had my heart set on an Alvarez, but there was this Martin in the store that I ended up playing. I disliked it at first, because it was so small and because it had flatwound strings on it. There just wasn't any brightness to it, which was what I was looking for.
The sales guy however told me that it was probably the nicest bass in Athens the time (this may have been a pitch, but now I believe him), and encouraged me to look at it a little bit more.
I had him put roundwound strings on it, and it came to life! It was loud, resonant, expressive and sounded good plugged in too.
It was actually used, but not by much--some guy had bought it and returned it something like the next day. He hadn't even taken the plastic off of the pickguard. Basically it was a free discount.
Anyhow, I've had that bass for just over a year, and it's been great to me. Wonderful for convenient playing inside or outside, and it gives you some opportunity to be heard if there's an acoustic guitar around, as opposed to sitting around.
Maybe more information than you wanted/is appropriate for this thread, but I highly recommend one if you're serious about it.