I sent them a couple hundred old slides. They scanned them, per my instructions, as 8 bit jpgs, and posted the images online for me to review. I could choose up to 20% of them to not have scanned or pay for. They were a little too dark, so I contacted their customer service and pointed out a couple that were obviously too dark. Two days later, I got an email with new versions to look at. I told them that these two were much better. They said they'd process the order.
About two weeks later, I got all my slides back along with 2 dvds. The first was, I believe, the original too dark scans. The second were the same images, but brighter or with more exposure than the other set. No extra charge for this. I brought them into Lightroom, and made some further adjustments/cropped, etc. I've decided to do the same with the remaining 45+ carousels. I'll then use those digital images to make a couple Blurb books to document all those years for family members. The images that are good enough for printing, I'll rescan on my Konica-Minolta scanner to try to sqeeze out everything I can.
It's probably not a good choice if your goal is to have them give you "fine art" level scans. But for the cost, and if you have lots, and lots, and lots of slides or negatives that you want to be digitized, I think it is a very good service.
Brad