If you get a sim that actually works from the start, i guess you are lucky. Just pray you are not unfortunate enough to ever have to deal with their customer support for any real technical fuckup at their end... they burned so much of my time I can never go back.
I bought a 24 month unlimited contract (which I don't like doing but I know the network is technically better so bit the bullet). The sim didn't activate, 1 months of phone calls and endless promise after broken promise, they still couldn't activate the thing. Finally they sent me a new sim but on the wrong 1GB/month plan, which apparently they intended to switch once activated, which of course they never could manage to actually do. So after another month they agreed to end the contract since they couldn't seem to actually fulfil it.
Oh but there's more.... 6 months later I find out they are still charging me for this stupid 1gb contract for which no sim card even exists. I reluctantly call them again thinking at this point it might be faster to open a law suit, this is ridiculously complicated and takes much convincing since the contract is now supposed to be ended so all the account numbers etc are wrong. They agree to send me a refund me by cheque for £50 rather than set up another DD to avoid more fuck ups........
1 Month later: I receive a cheque for 50p - fucking joke.
They still owe me £50, but it's not worth the time it would cost me to attempt getting it back.
This is partly why I don't like contracts, you can't easily walk away from shit like this.