A while back I received a free Premium membership for VocabularySpellingCity in exchange for a review of the program. It took me forever (whoops!) but here it is.
Overall, its a good online program. My daughter enjoyed the games, completed the activities willingly (which is always a plus), and understood how to use the website without issue. I was able to create my own spelling lists for her based on whatever we were studying, or words she was having trouble with. But I could also look up lists on the website and use the pre-made ones that had been listed. I also really liked the the activities included vocabulary activities as well as spelling - I think the two subjects are pretty inter-related so this made it easy to knock out 2 birds with one stone.
Here is my only issue - my daughter didn't remember anything. She played the games, practiced, everything, but at the end of the week, was clueless as to how to spell the words. I thought maybe its because it was on the computer and I was having her physically write out the words when I quizzed her myself, so I tried to have her do it on the computer instead. Still with typing them out, she got the majority completely wrong. Now, this could be something that is just connected to my child. She is a terrible speller - so another student might use the program and learn the spelling no problem. Now, the vocabulary she was able to retain (but this is something she doesn't have an issue with - her vocab is huge, she just can't spell it).
So all in all, I would say its a good program. It didn't work for my daughter, but I would be willing to give a shot with another child because I'm not sure how much of the issue was my daughter's learning style and how much was the method of using the website. If your child likes computers and doesn't have a really hard time spelling, then I would give the website a shot. I think with children who have spelling issues though, this program probably won't turn out to be the magic solution you are looking for.