The subject matter may have a bearing on how beneficial the course is (as well as a recognised qualification, mentioned earlier). If the subject is a "fast-changing" area module notes/topics may be out of date before you begin your year.
I did the B.Sc in IT with Oscail (DCU), completing it in 1997, and the courseware fell behind the rapidly changing IT landscape at the time - for example, there was no mention of the internet, and the programming language was BASIC (I know that has changed now, but it took a while!).
I'd second the other posters on the commitment required - it's tough to come in from a day's work (and commuting) and get stuck into study.
As one tutor described it to us - "As a distance student, you are trying to teach yourself something you don't already know". If you think you can crack this, then by all means do, and good luck, whatever you decide!