IMO it's extremely overpriced for what it offers.
If it was well under $1000, then I would consider it decent value, but it's about half the price of Invisalign for much less than half the value.
Invisalign works with some pretty impressively engineered software and attachments, Smile Direct has no attachments, so very little capacity to actually move teeth because they're anchored onto nothing.
Also, there's a very, very advanced skill to a clinician knowing what tooth movements will work, and which won't in the actual mouth. So just because a computer models a movement doesn't mean it's realistic. When you get Invisalign, your dentist goes over each step of the plan in detail and can chat back and forth with the Invisalign dentist in Costa Rica where the modeling is done. Often the plan gets revised multiple times before it's approved. Most experienced Invisalign dentists will have an ongoing relationship with their prefered counterpart down south, that's how much tweaking goes into it when it's done properly.
You get none of that with smile direct. No dentist looks at your case or reviews anything to do with your particular mouth.
Basically, you're paying a premium for a pretty shit product that only has the capacity to do minor movements, and with no benefit of expertise from anyone. It would be fine for very, very minor cases, but most patients have no idea how to evaluate if their own case is minor. Orthodontist friends of mine often tell me how the patients who think they're teeth are really bad are often simple, and the ones who think it's just one tooth that's crooked actually are complex.
So yeah, my assessment is that it's way, obscenely over priced for how little value it provides. You're much better off paying twice the price for several orders of magnitude better product, expertise, and technology.
ETA: a lot of dentists hate it largely because it's creeping in on their territory, but I don't give a fuck about that. I don't like it because it's criminally over priced. If it was closer to $500, I would think it's a fantastic product for people with truly simple, safe enough cases for it to work. Oh yeah...the safety part is a big concern...trying to move teeth in certain conditions can make you lose teeth. Definitely consult your dentist before doing it.