I had the 12 Ultra Slug at first.....it shot VERY well with home cast Lyman sabot slugs (510gr from wheelweights) running about 1500 fps.....3" shells. The actual weight of the gun made this otherwise punishing load tolerable, and I was quite able to sight it in at the range. It only took 5 rounds! But I found the gun was too heavy for my liking when it was time to go off stand and start moving around a little......
I then bought a 12ga Tracker II, which was pure murder on the shoulder with those Lyman slugs, even when I tried to load them down a little.....I had the bbl Pro-Ported (Magna-Port), which kept the fore end from leaping out of my hand, installed a mercury reoil reducer in the buttstock, and then went to a 1 oz Federal sabot (store bought ammo....), which gave me 5 holes 1 " high, touching at 50 yds, and a 2-3" group 2 " low at 100 yds. This from a sitting position at a shooting bench, resting the fore end in my hand, which was resting on a padded wooden rest.
I found this rig to be far more tolerable to shoot, not too much more than my 16ga smoothbore slug gun.
I've been hunting since the 2000 season, (I started kinda late in life, though I've always fished, and my dad was a grouse hunter...), and up to now, have always hunted on CT state land. In 2001 I got a spike buck with the Ultra Slug from a sitting rest under an evergreen at 28 yds. In the 2004 season, I got a good sized doe while SLOWLY moving from one area to another at a range of about 5 yds.
The Tracker II is excellent for the fast sight picture acquisition you need in the bush, like I did this past season, but I have the confidence to take a deer all the way out to 100yds with it should the situation arise.
The search for the next gun is a lot of fun in itself.......keep us posted as to what your choice becomes, and how it works out for you!