If its 'free' (they contribute, you don't) then go for it.
If its matching (you pay x, they pay x), and you aren't reliant on the money, and you want to increase your retirement income then go for it.
If its a top up (you pay 2, they pay 1) and you aren't reliant on the money, and you want to increase your retirement income then go for it.
Anything else, I'd suggest you avoid. Unless you earn ££££ from them a year I doubt it will make any difference. Tomorrow they might shut down and you could have £50 locked in until retirement. But £50 is £50.