I've done the OU A215 course and thought it was fantastic. However, I didn't like (or find useful) posting my work online for other students to give feedback. I'd been to a writing class before at another university and was used to giving feedback, face to face, in a group.
On the OU course we were given no guidelines for feeding back on each others' work, so some people were making comments along the lines of 'I really didn't like it...' without saying why. On my other course we'd been briefed on what to look for specifically (plot movement, characterisation, dialogue, etc.), and how to give the proverbial 'shit sandwich' if we needed to say something negative. The emphasis was on looking for something positive to say, while being honest about what didn't work. I found this very useful, but the online nature of the feedback from other OU students was another matter.
I did not find it useful to have someone say he thought a character in one of my short stories was 'ridiculous' without being able to say why. (Incidentally the tutor gave me 94% for that story so it can't have been that bad!)
Like a lot of online forums you get people who are more active than others and I found that some people (just like here on MN!) were frequent and vociferous posters and had 'fans' who treated their words as if they were gold dust, while other posters were virtually ignored.
In the end I only gave my work to the tutor and trusted critics that I knew from my previous course. I felt that if you weren't a confident writer the online feedback might be seriously demoralising. Frankly it pissed me off when people gave ill-considered or poor feedback. It's worse than nothing at all.
I loved the Saturday schools with the OU. Although not compulsory, I just couldn't understand why anyone wouldn't want to take advantage of such a fantastic resource. They were brilliant.
I'm planning to do the Level 3 OU creative writing course very soon but will probably stay away from the online feedback again.
Sorry this is a bit long!