I had a SE 4X4 Xterra with LSD. It worked great. I could always tell when the LSD locked in. Granted, LSD allows a certain % of slip before they engage, so some LSDs may be better than others.
The Titan ABLS is awesome. Just as with a LSD, if your on a smooth, level surface going straight, the wheels will have the same slip, so any LS action won't kick in. However, if the road is wet and your going straight or the road is dry and your turning, the ABLS will definitely kick in. I have seen it work countless times. All you need to look for is the ABLS dummy light blinking as a small % of slip difference is detected. I feel this system is excellent. It's also awesome to have it on the front axle as other trucks only have LS on the rear axles.
I had a '96 Camaro w/o the LSD. I left dual patches(when the darn thing ran right) on easier pavements. It didn't have the power to leave anything on rougher pavements as it got more traction. I thought I had the LSD at first until I realized I wasn't giving it any difference of slip. When the rain and snow hit, that's when I really found I had no LSD.
Have a good one.