I think it depends on quite a few things as to whether it's managable and you feel it gives enough balance. The commute, the flexibility, the hours themselves, how you think your child will cope, and their routine. I went back part time initially which was fine, but I had the same workload as I had before maternity but with less pay and the expectation to do it in less time. I found another job which was full time a month later and was so nervous as it was full time, but it's been great. It was very hard at first, and I think finding childcare you are comfortable with plays a huge part in that; we chose nursery, and he loved settling in days and I knew he was safe and being kept busy. Work now is only a few minutes down the road, I don't know if I would cope psychologically and also physically with a long commute, knowing it would take a while to get back if needed and also the sheer tiring nature of it- it's a lot easier if you are close by. My hours start early but I'm finished and home by 4pm, so still a good few hours in the evening together which makes all the difference, I'm not sure how I would feel about getting in just before bedtime and that's it, but plenty of people do and find it okay. He also slept through from 7pm until the morning which helped massively as I could relax in the evening, and then get a good night's sleep (it's tiring, very tiring- not sure how I would cope if I was also up and down all night).
It does become the new normal quite quickly, and he loves nursery, he also loves seeing me at the end of the day and I have found the time we do have together is better quality (as cheesy as that sounds). You have to find what works for you, many of my friends are much happier working part time, but I would look at different factors, finances, and remember that going part time doesn't afford you the chance to automatically go back to full time when you choose. If you can afford to drop a day though and you think that would make you happier, then no reason not to really. Or maybe start full time and see how you go? Either way there's not really a right or wrong answer, good luck.