Going from 0-1 was very hard, but DD had colic, reflux, the lot. I remember DH once shouting this is a bloody mistake, this child is ruining our life. Turned out DD was also on the autism spectrum which still makes life difficult, so I would say it also depends on your baby.
Going from 1-2 was easy, DS1 was a very placid baby, as is DS2 which had also made 2-3 fine (so far). Am on maternity leave at the mo, but plan to go back to work full time as I did after each child (took a year). At the moment I think the success lies in the gap between kids: DD is 6, DS1 4, DS2 10 weeks. This meant we were out of the baby age before the new baby arrived, each child independent but we still had all the kit and children can play together. It is school holidays at the moment, the older two play (argue) with each other a lot so that I can look after the baby reasonably well and don't feel antagonised by the baby's arrival or needs.
A lot of my friends, especially working ones who did not have age on their side went for the less than 2 years gap. To my mind they suffered a lot because they basically had two babies with very different needs, one going though the terrible twos and a newborn. They needed a double buggy whereas I just had a buggy board for a few weeks, the first still needed a lot of attention, maybe did not even know how to walk yet, the stress of feeding a newborn with a toddler putting fingers in plugs, or taking an hour to eat lunch. Makes breastfeeding difficult. We also had one year with two at nursery full time and it wiped out my entire salary, that was hard so I was glad it was not longer. Though Nursery is much easier as you get 10-12 hour days of Childcare all year round, which gives you great flexibility. This said, once kids are older they will probably be closer, I am very aware that when DC3 is 4 the other two will be 8 and 10, so not really into the same games, and when DD starts Uni the youngest will just have started secondary school.
Having children has not been the end of my career, I actually got promoted after my second child when I applied for a more senior position. My boss expressed surprise I wanted more responsibility, my response was that this showed how serious I was about work. To be honest, having two rather than one makes no difference, it is having the first that has made it a bit trickier because I needed more flexibility. Of course I can't be as driven as I would like and but as far as I am concerned I have another 30 years of working, my career will pick up again when kids are older as long as I keep it ticking along nicely. I am the only woman in my team with children, so as far as I am concerned, I am lucky, having my career and my kids.
As for social life, yes, having more than one makes it difficult because when they are young you can't eat out in restaurants with them and few friends can welcome a family of 4 or 5 easily. Personally since having our first, we don't have the time, energy, spare cash to go out, so we don't.
When I work I do the school run every morning and come home late 3 days a week (like 9 pm as I commute to London) so DH does the Childcare. I work from home one day a week and pick up kids from school another day so basically am home for kids two days a week so I cook and do the Childcare while DH goes to the gym after work. Saturday mornings he takes DS1 to football and then the shops, I take DD to ballet and cook lunch. I take all the kids Saturday Afternoon so he gets a break, he takes them Sunday morning so I get one, and we do something as a family Sunday afternoon. It is a bit staggered and ships in the night but it sort of works. The only thing we don't manage is the housework, I do all of it but badly, DH does none so house is a tip, so I really want to get a cleaner when I go back to work because weekends are chores central and it does mean that kids get a bit neglected. Just keeping on top of laundry for a family of 5 and making sure all uniforms & book bags are ready, homework is done and lunches packed every day is a task!