How do you approach being at home on your own with an infant, or with a baby and older siblings?
Dh just does the same as any woman, if not better. He looks after three children really well, and doesnt find it particularly taxing. He prefers it to working
Does it affect your sense of self, your approach to your career?
Dh isnt bothered about work really as it is a means to an end to him.
How do you approach things with your employer, and - if you intend to go back to work - what things can you do (or ask for) that help to make sure that your career doesn't stall or suffer?
He was going to take paternity but it hadnt came in at the time so he quit his job. He does full time care and I returned at 2 weeks.
What support do you need from the other people in your life, and what arrangements can you make (long term and day-to-day) that mean you get the most out of the time?
DH has no family help. He meets up with other dads and their children, especially one of his closest friends, and they take the children places in the day.
And just how do you identify the best baby-and-toddler groups?
No big deal to him. He attends soft play coffee mornings and that type of thing. He is rarely the only man.
Other stuff?
Nobody I have encountered thought it was strange. Dh has never been treated as he is incompetent, butI think it is because he is really good at parenting so noone doubts him. I would say there are times he is bound to be tidier than me, and I take that in to consideration. We started young so birth didnt effect me much and I definitely dont agree this would automatically make me more tired. I easily sleep when the newborn is, why wouldnt I? Same as having a baby hasnt made me incapable of working, going on nights out, going away with my friends or anything else. I had children, I am not dead
Nearly all previous posts I disagree with when thinking of our family Dh never worries about money or being the breadwinner, it isnt the 50s! 
He has lots of friends, and lots of people to hang around with but he is very social. We hang around with a lot of the people we always did and neither of us are baby bores, or ever had a conversation on nappy types or whatever you here people discussing on here. We just discuss going out, people we know, different takes on issues and stories in the media. Just the usual as you do with your friends.
Sorry for long post, but I cant abide the lazy stereotype of disinterested, incompetent dad, and baby obsessed martyr mother.