The basic functions of a Now TV Box work without a subscription. So, whether you pay or not, you'll always be able to get BBC iPlayer, ITV Player, 4oD and Demand5. You'll also continue to be able to get Youtube videos through the box. (It's a great way to watch them).
Further you'll be able to continue accessing radio channels from around the world (such as the wonderful ROK British Comedy Channel, with the Navy Lark, Round the Horne, Men from the Ministry, Hancock's Half Hour, etc) via the TuneIn app. (There are also some additional free special interest apps which you can add, and continue to use, available via 'Channel Store').
As you've probably found by now, the Entertainment pass gets you access to Sky1, Sky Living, Sky Atlantic, GOLD, Comedy Central, ITV Encore, FOX, MTV, Sky Arts 1, Discovery and three kids' channels. (It took me a while to work out how to find them though. Just in case you're still struggling, go to Now TV, up to Featured, right to Live TV, up to On Now and right to the individual channels).
It's worth noting that, due to licensing restrictions, a very small number of programmes can't currently be transmitted via Now TV (but they're working on it). Here's today's list of missing programmes:
http://community.nowtv.com/t5/Entertainment/Entertainment-Unavailable-shows-on-live-channels/m-p/139292