I have open diffs and still have done a few crazy trails. Especially on the slickrock, the traction is so incredible that you can go steeper than you ever thought possible. A locker would definately help, but you can have a lot of fun with an open diff too. I don't know what trails we will be doing, but in my little explorer with open diffs, 3" body lift, and 31s, I can do a lot of trails like Elephant Hill, Fins & Things, Kane Creek, Steelbender, etc. I even did Behind the Rocks. Don't let the name "Tip Toe Behind the Rocks" fool you. Its not an easy trail. It is Behind the Rocks with a bybass for the major spots like High Dive, Up Chuck, etc. I do not recommend that trail for a rig with as little modification as mine, but I still made it without the locker (taking the bypasses of course). But the other trails I mentioned above and several others that are very fun can easily be done in a rig like mine, and you have a better lift and bigger tires. So basically I'm saying, you'll be fine without a locker, or if you got the money and want to make it a little easier, go for it.