I don't have enough experience on a mountain bike to give much advice, but I have changed my tire selection and suspension set-up. The change is like having a new bike that hooks up much better on the trail in a wide range of conditions. A little attention to these details can make you much more confident out on the dirt.
There is a little new deadfall, but the trails are in very good shape. Not being a summer mtb rider, I was surprised that they've stayed so clear of encroaching greenery. The little rain we had the day I rode made the trail surface just about right.
On Merlin, there's a new reroute around a tree that fell last winter. A big "thank-you" to the little trail fairies that do this kind of work!
Unabashed, uncompensated, unqualified product endorsement:
I think my bike fit is pretty good and I'm comfortable enough, but one area where I have been dissatisfied is with my bar grips. I replaced the reasonably adequate factory grips with some lock-on Oury models that were a little bigger and perhaps softer. An improvement, but I still had some discomfort and had to shake out the numbness from time to time. That's easily done when cruising on the road, but single-track usually demands my full attention and both hands. Enter Ergon grips. Diane and I did a ride with their team a few months back at the invitation of Competitive Cyclist and I had been interested in trying their stuff. Once I knew about the grips, I started recognizing them on the bikes of many of the best riders I know and the grips were given universal approval. I selected the Ergon GP1, size large, from the many choices within the product line. I have pretty big hands (and will say nothing to quell the rumors about guys with big hands.) and I'm generally more comfortable with a larger contact area. I've got to say that these things really are at least as good as advertised! I was on the bike for about an hour and a half and never gave my hands a thought other than perhaps, "sweet".
These Ergon grips have added a new level of comfort to my MTB ride. Good stuff. Go buy some.