I hated every minute of it. I was the only one on my team with children and they seemed to think I'd been swanning about, living it up on "free" money (SMP) for nine months. I felt excluded from certain parts of the job, for example being asked with less than 24 hours notice to go to the Manchester office for a week and having to say no, "Oh, but we've already booked the hotel and the train tickets.......". In a lot of ways it felt like starting all over again. Before I went on maternity leave I was always chasing the next step and the next and the next, constantly pushing myself and I worked really hard to build a solid reputation as someone who could get the job done and get it done well. When I went back I felt like I was starting back from square one only this time I had additional commitments so couldn't do things like dick off to Manchester for a week with no warning or work until gone 8pm because something urgent had come in. So because I couldn't chase like I used to, I couldn't properly rebuild the reputation I'd lost while on leave and I just got more and more pissed off and unhappy. I was given a verbal warning for "lack of commitment to team goals" after taking a day off due to the baby being sick (couldn't send him to childcare) and another "discussion of concern" when we had bad snow and my childminder took the decision to close for the day and I had to take leave for it. I started getting left out of meetings and not copied in on emails, I would then get shit off my ma ager for "not keeping up" with the latest developments in whatever project we were working on. A senior manager said to me, very much off the record, that I made the decision to make myself less valuable to the team by going on maternity leave and that I had therefore made myself an easy target for the shit jobs and the snide comments from the rest of the team.
I got pregnant again very quickly, got signed off sick for the duration, and handed my notice in four weeks before the end of my maternity leave. I also filed a formal discrimination complaint
I've never been happier since I became a SAHM. It's not for everyone but it was the right decision for us. Nowadays I'm self-employed, working from home at the same time as looking after the DC.
I think you need to do what's right for you and your family and how well your return goes will depend on how much you like your job and how supportive your employer is.