Yes, it can be a drawback of LCD technology. The best approach is to find the set you like and buy it from a good retailer. Then, if you have any issues, you'll get looked after properly. I've seen very very few backlight problems and I've sold huge numbers of sets, but it is an issue to be aware of.
The 40W4000 is an excellent set. I would certainly try and look at one and see what you think, although if you watch a lot of sports the 100Hz is very useful.
There are lots of great sets out there but, to be honest, I'd probably be inclined to wait for the new ranges in March/April.