Hi,
I remember from previous questions that there are a few OU students on the forums, but they are probably too busy to answer you at the moment :)
As you may have guessed I am an OU student, ad have been for a few years. The OU year traditionally runs from Feb to Oct, which is why most students will be busy at the mo, although an increasing number of courses are now offered which start at other times of the year.
Generally, the amount of time you spend on a course depends on the level and type of the course, how much you know about the subject before you start, and how important it is to you to get the higher marks. Fitting it in can be difficult, at the moment I have a 1hr train journey (each way) to/from work which I use as reading time, but not everyone is that lucky.
Tutor support can be a liitle variable - I've not yet had a bad tutor, but some tutors are very 'hands on' while others are 'hand off'. Personally I prefer the latter, but I know of a number of students who have floudered because they need the sorrt of encouragement (and pestering about staying on timetable) that comes with the latter.
Very few of the courses I have studied are work-related so I don't bother to put them on my CV, so I'm afraid I can't help you there.