They are not recommended - I think because of the seals on cooker doors.
If you read the reviews on the Amazon Link ummmm, there is something on there about cleaning ovens.
I wouldn't get a cheaper steamer, they are just not as effective.
The main problem for me is getting the thing out of the cupboard and setting it all up. I have ceramic tiles through three rooms, so tend to wait until a nice dry day, open up the windows, clear the floors as soon as possible and have a steaming session. I quite enjoy it, apart from the getting ready bit. Really good for cleaning loos, sinks, tiles, kitchen units and little corners that you cant get into and of course you save on cleaning products!! You need to cut up old towels 'cos you need quite a few!!