If you get the legal, original, they appear to be not too bad, but too bloody expensive.
The cheap Chinese clones are suitable for plain code reading only, with limited live data. Definitely avoid any programming, including keys.
Somebody who should know better has gone and shagged their Corsa by trying to do some ECU reconfiguration, and now can't start it. So I have to pop over the weekend to see if it can be recovered. The silly tit was previously warned not to use the PoS for programming, but didn't want to bung me £20, so now is at the mercy of whatever I want to charge, if I can be arsed. I quoted him £200 in the hope he'd say no, but he's now desperate as he can't get the car to a dealer.
From knackered immobilisers and alarms that have been ruined with Chinese copies, I have about a 2/3rds success rate in recovering them.
I truly would urge not using it for anything other than code reading and live data (that its poor at anyway)