You won't get kicked off the network or put on a "bad boys pipe" no matter how much you download so to that extent it is unlimited. You will get short(ish) term volume dependent throttling - http://my.virginmedia.com/traffic-management/traffic...
NNTP and P2P will be subject to shaping during peak times although I've heard that it isn't overly difficult to evade that (possibly as simply as using encryption with NNTP).
Where there can be a problem is if you aren't the only person intent on downloading the internet in your locality. Cable supports high headline speeds but the local pipes serving a fe hundred customers are skinny indeed at 8x50Mbps down max and 2x18Mbps up max - as you can see that won't really support too many people seeding torrents 24x7 and just a coupe doing that wil cause considerable local congestion.
VM's peering isn't too hot either and there are constant complaints about buffering on youtube.
Gaming - the jitter can be horrible.
Your call - if you don't like it you can quit without penalty during the first 28 (or maybe 30) days but beware that they will try to delay you past that deadline if you try to bail out.