I am using them. I sent a lump sum of cash over from my other HSA for investment purposes, retaining my old HSA for any normal expenditures, a few months ago.
Setup and transfer of monies involved a series of emails and electronic forms. It was fairly painless, but a slow process that took a bit of time. They will necessarily send you a card, but I destroyed mine since I don't plan to spend money from this account. I had a number of questions during the process and their representatives were responsive and helpful.
After I set up the HSA, I believe I had to jump through additional hoops to turn on investments, which is via a TDAmeritrade account. I forget if I made this account of if they did, but it has my preferred login handle. TDAmeritrade has a terrible password policy though which none of my passwords conformed to, since they disallow special characters. I also had to jump through another hoop with TDAmeritrade to turn on commission-free ETF trading. This allowed me to invest in VTI without a commission.
I am not a fan of the TDAmeritrade website, which is cumbersome and seems like it encourages day-trading.
While the Lively website has improved significantly from what it was, it is not great. Previously it lacked detail and visibility into your accounts and such, which has improved. However, in my opinion the site is quirky/cumbersome and seems like it is intended to be used on a phone rather than through a web browser.
At the end of the day, the whole thing is on auto-pilot and I don't look at the sites anyway. The service seems to be working out fine for someone who just wants to passively invest their HSA monies.
Since then, they have debited my linked bank account for $2.50 each month and sent a receipt of this transaction via email, which is the cost of doing business with them. In that time my assets have appreciated a few thousand dollars in a few months, which is preferable to the $375/year I would have received in interest previously.