We're just about to move into a house which doesn't have a phone line or cable connection (as far as I know) and as we won't be needing either and don't know how long we will be staying (it might be a couple of months, it might be a year or more), some kind of dongle arrangement seems to be the best idea for servicing our current internet needs.
We aren't mega users - mainly FB/MN/email etc. plus a bit of i-Player.
The guy who lives in the house at the moment uses a T-Mobile dongle and is quite happy with it. Unfortunately, it doesn't support Skype, which is our main "telephone" (apart from our PAYG mobiles).
Find out the coverage before you commit! Many areas have black spots. I know a few people who bough into a contract and then found that they had naff reception. In the area I am in home phones are the only way to go as even O2 and T-mobile have iffy reception and dongles cannot connect! Less than half a mile away reception is fine. Do your homework or it could be an expensive gamble!