The last time I read about these, the big issue was cell degradation. A normal panel has a life span of around 20 years. These have a life span of 5 years, or less. if they can overcome that, awesome.
That would definitely be a deal breaker. I'm sure they won't be cheap.
New tech always is. It's why I hope SMRs can get a foothold. They're gonna get a bad rap early on because of cost (and potential design flaws, those remain to be seen), but if we can start dropping them in a few places globaly, the costs will go down significantly since they can be mass produced.
Now that would be real cool.