As the only good choice so far there isn't a lot to add for a review. I wish this was more actively developed but, I don't think there is a strong demand for online greeting cards any more.
WebCards does work. There is a free option, older software which does still work. Or, you can make a one time payment and have the premium version with a few extra features. If you want to sell your greeting cards, the premium version is necessary. If you just want to offer your art on web cards/ ecards for free, then you don't need the premium software.
I wish the software worked a little smoother but overall it is good. Even if it is the only option worth reviewing, it is still a good way to showcase your art and get people sending it to each other, hopefully.