As a proud LR3 owner (which the LR4 is very similar to), I would say the LR3 is quite reliable. Certain parts are prone to failure, but in a predictable fashion (the control arms, and air suspension will fail, but you expect it at around 80,000 - 140,000 kms). The engines, both the V6 and V8 were rock-solid.
The LR4 corrected those issues, and to my knowledge most owners are very, very happy with this vehicle.
I live in BC and regularly take my LR3 off-road and I see many doing the same. The only reason I purchased the LR3 was because I have a family (need seating for 7), but love going off-road. In that market there aren't too many options, and nothing that compares to prowess of this beast. I tried a Suzuki XL-7 and a Toyota Sequoia but I fell in love with this.
The only other thing I would object to is referring to the V6 in the LR3 as an 'underpowered huffalump.' I actually chose the V6 because it had a proven record for reliability and it actually quite well-suited to the LR3.