I have an '08 with 35s, which is the also a 3.8. Because you are manual, you can definitely get by if you don't want to or don't have the funds to regear. 6th gear will be completely worthless except on the steepest downhills with a tailwind... I ran this way for about a year if I remember correctly. Coming from a 5spd, it wasn't a big deal. And because of the 4.1 transfer case, I was probably pretty close to the 1st gear gearing on my past TJ, which I was use to.
I then re-geared to 4.88s. Much improved, everything taking less effort and I can use 6th gear on the highway. I feel top end improved as well, cruising at 75-80+ regularly. Speed obviously takes effort in these bricks, but it can get there in most circumstances. Even more improved is the 1st gear low range. You can actually let the computer idle up the steepest stuff again.
Maybe I am spoiled, but I have to disagree with a lot of the comments on here. IMO, our jeeps are grossly underpowered compared to most any other vehicle out there. Unless you have a supercharger on a 3.6, or a 5.7 or bigger 8, you are hard pressed to claim your jeep flies..... Granted for the type of wheeling most of us do, more power is not going to add more utility, or make them go more places.