Amongst the current collection of guitars I own is a newish J45 and it is fantastic. It is the standard mahogany version, possessing a lovely dry, but sustaining tone, with a great low end thump.
Already having 25+ very good instruments, of which a few are in constant use, I was not shopping for another guitar when this one caught me unawares. I was actually checking out some new Avalons on behalf of a friend when I happened to pick up this sunburst J45 while waiting for some figures on the Avalon deal. Half an hour later ,I was heading out of the store with the J45. To be honest, I am not easily bowled over by many guitars these days regardless of maker or the price tag, but guitars like the J45 I picked up that day are too rare to miss.
A few more plus points for the J45 ( for me anyway )are the 24 3/4 scale length, very light weight/nice balance on the strap, very comfortable neck profile and the 44mm nut which makes it a good all rounder for fingerstyle and flatpick work. Oh yes, it also has a Fishman matrix pick up factory installed, which while not the world's greatest is very useable ( I did need to do some sadddle work to deal with some minor string to string imbalance ).
I have heard people talking about variable quality regarding Montana Gibsons, I can't comment as I seemed to strike lucky first time with this one.
By the way Martin Gibson, try to checkout a Lowden or two sometime, preferably a big O series body, these are miles away from the traditional Martin sound ( alot more overtones as opposed to the fundamental), but they are tonally incredible as well as being beautifully built. I have an O25 ( cedar/rosewood ) and an 032 ( spruce/rosewood ) the latter being potentially the loudest cathedral of a guitar I have ever played.