I was looking at thise and wondering, it appears that they are all Califonia concentrates, not as big as some of the other Kit producers...
It's probably crazy to be kicking this thread back up to the top nine months after it died of disuse, but since no one else who chimed in had actually made one, here goes:
I did a William's merlot kit for my first kit. Started it almost exactly two years ago. Aug. 1, 2008. It made a pretty respectable if unspectacular merlot. (I still have a couple bottles left to try at two and three years.) Most casual wine drinkers like it fine. To someone who's used to trying and assessing a lot of different wines, it may seem a little simple and one-dimensional.
As far as the kit goes, it is by far the simplest one I've made. The directions have you mix water into the concentrate, dump on the yeast, rack in a month or so, then bottle a few months later. Note there is no degassing called for and no stabilization routine. Presumably it has enough k-meta in it to see it through a couple years in the bottle.
One big plus: This is the only kit I've seen that makes a realistic timeline part of the basic directions. They say to bottle after about 6 months, then wait another 6 months to one year before drinking. Don't you wish other kit makers would be so honest?
When you look at the amount of concentrate and the amount of water added, remember this is pure concentrate, unlike most kits, so adding that much water doesn't give you a diluted wine.
While I've made about 15 more kits in the past two years, I have not made another William's kit. That's partly because this is a hobby for me, and months of doing nothing doesn't give me the feeling of accomplishing something. But at $2.50 per bottle, I would not hesitate to get another one based on the cost and results. It's also a great company to do business with (I know from my beer brewing days).