Being able to take ages getting ready - shower, hair, nails, moisturising, reading a bit of a book, make up, get dressed, all at a leisurely pace without feeling enormously grateful to DH. Now if I want to do that he has to wrangle the toddler while I do it, which means I feel like I owe him the equivalent 'free time' allowance, nothing is ever entirely guilt free!
Spontaneity and being able to stay out late on a whim, although we can now do that, just not both of us at the same time. We are lucky with family nearby so we have it better than most but still have to plan everything in advance.
Smoking 
Spending money without really thinking about it or worrying about it or guilting about it
BUT I absolutely love being a parent, and the things I miss are absolutely minor compared to the thrill I feel on my way home from work knowing I'm about to get a cuddle and a sloppy kiss and a huge smile and 'mum mum mum mum mum'.
Don't let this thread scare you, if you asked 'what do people love about post-baby life' you would want to get pregnant tomorrow 