I'm currently on my second module, studying part time.
Funding is by student loan for me - it is about a third cheaper than 'brick' universities (in England, anyway) but of course you don't have the face to face element (or as much of it, anyway), however you can study without prior qualifications whereas in a brick uni you would likely need these or do an access course.
Number of tutorials and means of delivering them vary module to module. Generally seems to be about once a month. In my first module their was a choice of face to face at various locations around the country (and quite a few at that in England - coverage a lot poorer in Scotland and Wales!) but this module has more online tutorials and only three opportunities for face to face, these being longer 'day schools' that take place between ten and three.
In terms of difficulty, the first module is very much geared towards people who haven't necessarily studied formally for a long time. They also have lots of short study skills courses you can access whilst waiting for your module to start.
My understanding is that it starts off at a gentler level than a traditional university to help bring those who haven't studied for a long time up to speed, but it soon catches up. There's quite a few on my course in that boat and they have on the most part been fine. The tutors are understanding that you may need additional support with study skills.
Time - I found it really variable. On my modules they divide the study planner into weeks and it's a chapter a week. However some weeks seem to take a lot less time, some weeks much longer - I averaged between 10 - 15 hours a week, more on assignment weeks. You do have to be quite disciplined and fairly self directed.
On my modules, there's been an assignment each month approximately, and then either a longer assignment called an EMA or an exam at the end - happily, on the degree I'm doing there's only one module with exams. I think some modules have online tests etc too.
I'm quite a solitary person so haven't found it particularly isolating - there's forums and most modules someone will set up a facebook/WhatsApp group. I'm not generally huge on social media but have found the Facebook group a blessing - just having the shared experience! Much to my surprise I've actually managed to make a couple of real life friends too.
My tutors have been great so far - emails replied to within 24 hours, good explanation and constructive feedback on assignments, and a reasonable turnaround time for marking. I do hear some horror stories though so I think there is an element of luck of the draw.
Thus far it has been an overwhelmingly positive experience for me.