Oh gosh, I know exactly what you mean! I'm a real nester, it irritates me like crazy that I can't repaint or refloor my flat >< I want walls with different colours instead of just cream like they always are when you rent, I want nice floors instead of the horrific carpets they always seem to choose, I want a garden I can dig up and rearrange and plant leeks and climbing roses in, I want a bathroom I can redo, I want doors I can put catflaps in, I want rooms I can extend, a loft I can put stuff in... and you know what, I'd really like to be able to hang picture on my walls. You can't put nails in a rented wall =[
I'm looking forward to being able to do what I want with the space that I have. I'm NOT looking forward to all the household maintenance. As much as I hate it, I hate being price gouged by plumbers and electricians even more, so I'd inevitably end up doing it myself. Then if I get married there's all the stuff the wife is going to want. New carpet, new light fixtures, new appliances, repainting, etc. And I'm almost certain to end up doing a good portion of that myself, because I am a cheap bastard.
Sometimes I think life would be so much better if I could just get a kick-ass internet connection installed in a cave somewhere.
I'm looking forward to being able to live with my boyfriend instead of having to be long distance. It'll just be nice doing the everyday things together :) Also we'll get a second ferret to be friends with the other one, and hopefully a cat if I can find one I'm not allergic to.
It'll be nice to have a space that we're in charge of and can do what we want to it.
privacy, decorating everything... I am about to get my first own place myself...but PLEASE don't get a dog when you don't have the time or the space for it... it's a bit different than a cat!
Like what you mentioned, the freedom to do whatever you want to your house. Decorate it and furnish it as you like. Starting from scratch - designing the layout, painting the walls, picking out the flooring, the little details like molding and light fixtures. My house is going to be spotless and gorgeous, that's for sure.