Yes... and no.
I've tried quite a few, some are still pretty basic:
Solvino, the Spanish grape concentrate that comes in a tin. If you make a straight wine from these following the instructions it will taste watery and thin. The best use for these I've found is a cheap source of grape concentrate (many recipes call for this).
Vigneron Carafe 21, the bog-standard 3-week kit. I think this hasn't changed much, you get what you pay for.
...but some aren't:
Beaverdale - huge leap in quality over the last few years. Now come in 6 & 30 bottle kits. One of the new breed of pure grape juice kits where you don't add sugar. These you add a little water. Good mid-point kits. Drawback is that quality improvement means price increase - they work out about £1.60 a bottle for ingredients. Once you add in your time you might consider finding a cheap source of 'real' wine works out better value.
Vintners Reserve & Other Premium Kits - these are straight juice, you don't add water or sugar. Mostly in 5 gallon kits at around £60 (yes!), so works out at about £2 a bottle. I've tasted some a fellow wine club member made. They are very good, but they taste like many £2.99-£3.50 bottles found in supermarkets. So add in cost of corks and time...?
On the whole you get what you pay for with the kits IMHO. See if you can find a Home Brew shop where they've made some kits up as samples for to taste.
I've also tried beer kits and they've gone the same way and some are really good now.
Happy brewing and listening for that blub-blub through the air-lock
