There are several OU threads that you might find useful if you search.
All of my module content is online, this is both good and bad, they have imbedded videos and interactive activities and it's easy to search for info you need for assignments but staring at a screen for an extra 16+ hours a week after work isn't great and the ebook versions are obviously missing all the interactive bits so you have to go back and redo those bits.
My experience for science ou degree:
Module 1 Level 1 is easy, GCSE level and to get you back into the swing of studying.
Module 2 Level 1, a lot more content and more A level contentand year 1 uni. Both level 1 modules have lots of self reflection questions so easy to pick up marks for assessments.
Modules 3 and 4 Level 2 expectations seem similar to first two years of normal uni, more independent research required, some group work which was conducted over a wiki and through the module forum.
Level 3 I'm about to start, appears more independent research based.
Assessments
Generally 5 assessments per module then a bigger one or exam at the end.
My last unit each assessment was worth 12% and then the last was worth 40%
Previous units the have been worth 10% and 50% for the last one and on one awful module the assignments were only worth 3% which was massively time consuming for such a small amount and the rest was made up by the exam.
Support
There is support available, I haven't particularly used any though. There are various forums both for your tutor group and for the subject. You can contact your tutor some are better than others at responding.
In terms of value to employers, I was encouraged down this route by mine, they give me study days and lots of other staff members are also doing them
Would I do it again? Probably, I'm bored of it now, I've been promoted at work since I started it and find it a lot harder to juggle work and the content and it's more a means to an end right now.
The OU offer free courses through Open Learn, they are excerpts of current or old courses and will give you a good idea of the presentation and what the content is like.