I got this for streaming my Netflix account on my TV and it's very quick and easy to set up. It comes with a lot more channels than I realised so if you like lots of old/classic movies you'll get access to hundreds on here for nothing - there are a lot of free channels which deal with classics/old sci-fi/old musicals/old westerns, etc. Some of these film channels are available right out of the box but for the others you just go into the channel store on the device and select what you want. They should be available within a few seconds.
Realistically I expect I'll mostly use this for Netflix and BBC iPlayer at the moment, but I expect at least 4OD, Five catch-up and ITV Player will sign on before too long. Even if not though I'm more than happy with the available channels for the money I've paid.
You do need access to a computer for the initial set-up/registration of the box. It takes about 4-5 minutes to complete and you don't need to go online after that as you can do everything else directly through the box. You'll also need to log card or Paypal details on the Roku site when you register - this is so that you can, if you want, select any of the paid services (such as some of the more recent films or some of the games). You can however set a pin so that you don't ever buy films by mistake (or you'd kids don't), so it's not really anything to worry about, and at least it's there if you do decide to purchase something extra.