Does anyone have any experience with the Hummingbird 596 HD DI? I'm thinking about buying one for the front of the boat and looking for any pro/cons for that unit. I already have GPS at the console but would like to try the down image.

I wouldn't buy a fish finder with down imaging that did not have side imaging as well.

What he said ^^^^.

I use DI 2% of the time, SI 98%.

unless you fish a LOT of deep water di is not gonna be a useful tool on the tm, si is but you have to remember to keep the tm still long enough to get a good reading.
I had a 797 di/si and then an 898 di/si on the bow and went back to a 788 with quad beam. the 788/quad beam is like poor mans side image but perfect for the bow I think, it spots fish and shows structure but not in detail like si. it is much cheaper to install too. one other advantage I got is I now have gps up front to mark spots, built in gps antenna so no puck and it will take 2 cards one for navionics and one for waypoints and recording.