Heya
Im in same position as you, so glad that you asked this!
When I went for my second interview, I was able to speak to someone who was on the SCITT course at that time and see how he was feeling about it and so I'll share that with you as it was enormously helpful.
So the following is basically generalising what he said:
Everything was to his own pace, there was a girl who was teaching full lessons within a matter of weeks, he still wasn't confident enough so stayed on just starters for quite a while. Obviously after a certain point obviously they have to start pushing you forward but apparently this is only done after tons of meetings and guidance, they went through and figured out why he wasn't more confident etc and worked on that together so his first few full lessons were done with 2 teachers effectively and by the time I met him (end of Nov) he was justt starting to do the full lessons on his own with minimal help, obviously all SCITT courses will have a rough guideline as to when you're expected to be doing this that and the other but you can speed that up whenever you feel ready, or slow it down provided you can give sufficient reasoning for it.
He has a wife and a little girl and said that he rarely got the time to spend with his wee girl but that was more due to his own perfectionism (he said he would complete a piece of work, and then obsess over it for a few days until he was 100% happy). He loved the amount of support he received, he had a mentor, tutor and then the course co-ordinator so effectively 3 mentors and had meetings with them regularly.
The work load he is managing, he said one huge bonus about the SCITT is that you do less essays than a uni based, so we only get 4 across the year but they do have hgiher word counts. But the bonus of it was that you recieve all 4 essay titles at the beginning of the year so you can effectively start them whenever you want, as long as they're handed in on time, plus it helps with citations (any that you can save and repeat etc) which is also very helpful.
A further help was that he was at the school from day 1. He said that had he gone to uni for a few weeks, and then the school then he reckons the other teachers and students will see him for what he was, a trainee teacher/student whereas being in the school from day 1 means that the pupils actually recognise him as a teacher or teaching assistant and treat him thus. He found it much easier to keep a professional/working mindset rather than switching from student - worker mindset.
Hope that helps, I wish I had noted down his email address if I'm honest! He seemed very calm and genuinely very happy with his choice but also very free to admit that there are of course those odd days where he drives home and wishes he just had a 9-5 job which to be honest, all teachers (whether in training or not) probably feel every now and then!
Speaking to him is what helped my decision to go for the SCITT course rather than uni based and caused me to accept the SCITT with the Chiltern Training Group and reject and offer from Greenwich.