Val Thorens is a great resort, high in the mountains with spectacular views and pretty much guaranteed snow. It's got a huge variety of pistes for all abilities and if you're looking for a snow sure resort then it's the place for you.
If you get the Three Valleys pass you can ski over to Meribel then on to Courcheval in a day but head out early and pick your route carfeully if you're beginner / intermediate as there are some exhilerating reds down to Meribel. This is well worth doing!
However, Valtho can almost be too snow sure! When we went March 17th '07 it was pretty much whiteout conditions for the whole week which can knock your confidence if you're not a pro.
As far as the resort goes, the architecture is not particularly pleasant and doesn't have much character but the accommodation is generally comfortable enough.
We stayed at Les Balcons 3 catered chalet but ate out a couple of times in the week as the food was a little bland but perfectly edible. I would recommend eating at La Cabane beneath Les Balcons towards the top of the resort. It has a more traditional feel with great food and friendly service!!
There is a huge array of mountain restaurants so you're never stuck for somewhere to stop and have a break.
The sports centre is pretty good also with all sorts to do including a swimming pool, saunas and turkish steam room which is a must for relaxing after hitting the slopes hard!
The majority of the apartments are ski in/ski out and you can ski pretty much straight through the resort thanks to very conveniently positioned snow bridges!!
In short, my other half (the hardcore skiier) would go again tomorrow but I would personally sacrifice some of the plus points here and go for somewhere with a bit more soul.