I’ve been on Giffgaff for quite a while.
O2 reception in all the places where I spend any amount of time is very good so I’m sorted there but of course YMMV.
I have an auto-renew £10 goodybag each month which the 250 mins, unlimited text and net. I use a lot of data but hardly touch the minutes so it suits me. They dont allow tethering though.
One little quirk of the system I found was that if you buy a goodybag or gigabag then it last for a month. If you use up all the allowance then you still can’t buy another one until the month has elapsed, only normal credit.
Customer service via the forum is woeful too, contributors get ‘payback’ by posting on there (regardless of whether or not they’re actually saying something useful) so ask any question and you just get dozens of people parroting the same useless things without reading what’s been said so far or even the original post. Infuriating. You can still ask an actual giffgaff agent though. But that’s not instant.
Also there’s a customer consultation going on at the moment where the price of the £10 goodybag (the lowest with unlimited data) is being reviewed and will probably end up being changed to either £13 or £15.
Other than that, it’s all good.