I thought I would chuck my tuppence in. I have one of these and I paid £12 a couple of years ago. I use it for work and check fryer temps with it. You do need to be careful you don't get spurious readings though. Clean oil won't read right as it doesn't emit as much infra red energy as the darker dirty oil. I check it regularly with an accurate probe themopen.
You can prove this by aiming it at a boiling stainless steel kettle, mine reads around 46°C when it's boiling. The darker the surface the better, so a nice bark on your best Brisket should be near enough to be accurate.
For that price I don't think you can go too wrong, its worth a punt.