payment gateways other than PayPal
custom sizes/resolution images for sale
multiple pricing for various size downloads
no public user forum on their site
based on other reviews, it seems support is either lacking or unhelpful. (I have no experience so I can't speak from anything other than what I've read.)
It's a shame really...it looks like a wonderful extension for a very reasonable price....but it appears to be missing some very important aspects that are necessary before considering usage in a commercial endeavour.