I love this Plugin. I have been using it for over 5 years without issue. I have used it on a number of different scenarios but mostly;
1) client sites that sell tee shirts
2) client sites that sell digital downloads
What I have observed is that e-Commerce is hugely complex and with that so are all the different permutations of what different people might want to do. Its just silly to attack a Plugin that doesn't work for you because its lacking a feature.
Sometimes this Plugin will work for your needs but sometimes it won't.
The support / premium support that WP e-Commerce Plugin offer their customers improved 100% in 2012 year and the benchmarks are that this is the most optimized and fastest of e-Commerce Plugins.
If you want to sell lots of Products then the WP e-Commerce Plugin is the one for you.