I run a 930 - not the JM Pro version, but I have modded mine to have some of the same characteristics while changing some things to suit me. I think based on mods, ease of shooting and combinations out there, it's hard to beat at the price. It isn't the most popular (I think because of some of the initial issues that the 930 is infamous for) but the guys who have them running good run them very well.
I did use a pump initially before I switched to the 930 - there are some advantages in loading (no thumb catcher like on the 930) but you just can't be as fast pulling the trigger. The other thing you can't do with an auto is easily mod the buttstock - like doing a Knoxx on a 500, etc. It is good enough, however, if you are using your 590 for other things as well.