I've done two online classes - Recallers (which obviously isn't agility specific) and Agility Fix-It through Agility U.
I wouldn't do a class like Recallers again. I find it hard to motivate myself when I'm one of hundreds and there's no way to get one-on-one attention. The information in it is fantastic, but it could have been a book and I would have gotten the same amount out of it.
I LOVED the Agility U class, and would definitely take more if I had more money and easier access to equipment. My particular "fix-it" was stuff that didn't need any equipment at all for the first few weeks, and then pretty limited stuff (you were asked what you had access to at the beginning, so exercises could be tailored to your situation), but it was still hard to do, and I felt like I was intruding on friends when I went over to their houses to use equipment and tape. I also drove around with a tunnel and jump in my backseat for a couple of weeks and would randomly pull off into fields or empty parking areas to work. I'm amazed I wasn't arrested for filming, or at least questioned!
The class was pretty small (12, maybe?). You had your own thread in the forum where you posted all your stuff and got feedback. The feedback was fast - if I posted one evening, there would be a reply by early/mid morning the next day, with a few exceptions (weekends) where half the time I think the instructor was replying from trials. That level of specific, individual feedback was perfect to keep my motivated. I posted probably 3 videos a week for the first half, where it was mostly games and such I could do easily with no equipment, and then once a week or so after that (often a montage of a couple days worth of work).