I'm definitely happier overall than I was when I was married, however it is more stressful in many ways.
For me it's that the responsibility for absolutely everything is always on me - every single school pick up/drop off, every household chore, all 'life admin', the financial burden of being sole breadwinner (exh does pay maintenance but of course it's not enough), the responsibility of being essentially two parents in one, making all decisions alone, managing the issues the dc face alone, if I'm ill it makes no difference I have to carry on, there is no one to take over, there is no relief or let up at any time - unless I pay for childcare.
Exh has very little contact (his choice) so the dc are with me 24/7/365. I have no family nearby so that makes it hard. I also have a stressful job.
Yes it is lonely sometimes, particularly in the evenings when the dc are in bed, or over the school holidays when I work from home and I can go days without other adult contact. Holidays away are lonely and can be more stressful.
However, the plus side of exh not being interested is that I don't have to deal with co-parenting issues really as he just leaves me to deal with everything.
As the dc are getting older it is getting easier in some ways as they can help more with chores and friends often comment that my dc are much more capable/responsible/helpful than theirs are - by necessity to be able to cope I have had to have them doing basic chores from an early age.
The three of us are a close knit family and it can be lovely having time together, again it's better as they're getting older.
I do find socialising difficult - I always have to pay babysitters and that puts me off doing casual get togethers etc. I always have to go to events etc alone and that can be hard particularly as I'm an introvert.
Managing the dc's upset and emotional stress as a result of exh's attitude to them is difficult as well and you always have to maintain a positive attitude about their dad (even when you're furious with him) as well as supporting them.
I think a huge amount depends on your personal set up, how much time your exh will have the dc, what the relationship with him will be like, how much family support, what your work/house/school set up is or will be. I do have good friends to talk to which helps.
Before I left exh I spent a lot of time working out and planning finances and practicalities - how would I manage school drop offs etc, where would I need to live in order to make work/school etc work.
Despite the stress and hardship sometimes I'm so glad I made the decision to leave and I wish I'd done it earlier.
Good luck with whatever you decide