Been with them since Metronet were bought by Plusnet (as have my parents).
Does exactly what it says on the tin (no frills & no shaping).
I would definitely recommend them so long as you are aware of the PAYG nature of the service.
Both upsteam & downstream is counted as far as usage is concerned, there is no usage cap per se, but you will be charged approx £3 per 4GB that you use above the inclusive allowance (note you pay in 4GB blocks, so if you go 1 MB over you pay for the whole 4GB & it doesn't carry into the next month).
These charges are in arrears but if you know you will go over in a given month you can buy 10GB blocks in advance for slightly less. Again they don't carry over into the next month.
Ultimately not a service for people who want to download the internet, but one that seems to be have a solid business plan behing it.