I really like my 4.5" lift. It was rough for a while, I think about 18 months. But it got real smooth when the springs broke in (the rears take that long to smooth out and get used to the weight I think). Install was very straight forward...we took 2 days and our time and had no snags. More needs to be disconnected from the front, and possibly the rear, to get the install done a little easier. Spring for quick discos though for the front, it's worth it. I have no vibes really from the lift, I think it's more towards the tires and wheels.
Note:I took the jeep out in FL for some spirited trail running at speed, and I broke one of the leaves in the passenger rear (jumping). It still rides great and had no effect on handling, but the pass rear side is about an inch lower than the other 3 corners.
All in all a good lift for the money. That being said I'm building my own lift on the 2door when I build that XJ up. I have a SYE and TW driveshaft but they're in the garage...just got them as a precaution when I bought the lift and never installed them.
Other note. the ride with the RC springs is rough. I put a set of BDS shocks on and it helped quite a bit. I also bent the driver's rear shock on the maiden voyage of my jeep with the lift on. I wasn't thrilled about that. The shaft on the BDS is noticably thicker and all my shocks have yet to have any issues after me beating on them repeatedly. Just m my 2c
Final note: They advertise that you can run 32" tire with 3.75" BS wheels. I tried that and it takes some trimming of plastic to be able to flex the lift out with and without the front SB connected.