0-1 was hard - initial short, sharp shock, but soon adapted. DS1 relatiely easy though (although I didn't realise it at the time - only in hindsight after the screaming nightmare that was DS2!).
1-2 a total nightmare. DS2 VERY difficult baby (and toddler). At least when you only have 1, there are times when you have a bit of peace because they do nap. But then if you have a second, the times they are napping you are spending with your slightly neglected 1st!
Suppose it depends on the age gap too. Only 2 years between mine. Whereas my sister's got a bigger age gap between her two, and whilst her eldest is at school, she DOES get a bit of "me" time when her baby is having naps.
2-3: after DS2 we won't be having any more. (he is lovely now at 3, but by god life has been tough with him).