Another thing that worries me slightly (any reassurance appreciated!) - you end up with lots of £10 transactions on your bank card to dodgy looking bookies. Could this negatively affect your credit rating or trigger any automatic fraud detection? You look like the worlds worst problem gambler.
I haven't joined Profit Squad, but I do a bunch of matched sign up offers when the mood takes me - probably made about £100 total. Things I find annoying are t+c's that are unclear - e.g. Boylesports has a £20 free bet but its given as 4 x £5 over 4 days, to be used within 7 days of account...