Actually, i've been testing and accepting LN payments on my demo site for quite a while already...
I personally find eclair mobile pretty user friendly. Offcourse, there's still a learning curve that's far bigger if you compare it with visa. Afterall, everybody has seen their grandparents, parents,... using VISA since they were born, so the visa-learning curve started allmost at birth. This offcourse isn't the case with BTC/LN.
Basically, you have to incentivise your clients to:
- 1) Install a decent desktop wallet on their pc
- 2) fund their desktop wallet with a couple hundred bucks worth of BTC
- 3) install a LN client on their mobile phone, create a new address, fund the address with "spending money"
- 4) open a channel between the client and the store's node, fund it
After these 4 steps, a store can generate a lightning invoice (QR) and let the customer scan and pay straight away... Works flawlessly, but still, i don't see my mother performing these steps...
Also, the fact that you'd have to close the current channel if you wish to open a new one (when you have insufficient funds in your current channel for planned expenses) is a drawback.
You can actually skip step 1, and switch step 2 and 3 (create a LN wallet right away, create a deposit addy and fund it straight from the exchange), but i would discourage anybody to keep a lot of funds on a mobile wallet.
The biggest "drawbacks" would probably be to get somebody to visit an exchange or some other seller to exchange FIAT to BTC...