I've had two.
The first slowly persuaded my mother she preferred being indoor than out, and at one point had the run of the house whenever someone was at home (being shut in the garage, but free-rein there, otherwise). Her freedon was curtailed somewhat when my mother got fed up of her tearing the wallpaper from the walls of every room in the house, but she'd still be allowed to go through the kitchen into the lounge.
She was great. Very independant-minded, loved the cat, was great fun. I have great memories of homework sessions being interrupted by her throwing herself onto my lap, jumping off, then jumping up again! She'd always wee in her hutch, though would poo wherever she felt like it!
My second just lived inside during the winter. Her 'home' was under my bed, and there were always pellets under there, but she'd always wee in her litter tray (though she was v particular about that - was happy with a laptray and a rabbit corner tray, but disliked the cat one I tried her with and pulled it out of the corner to wee on the carpet - great!). She was a rescue and had likelly been abused in the past, so spent most of her life in what I called 'scared rabbit mode' - she would come over for a stroke but wasn't effusive in her affections. There as a period of about 6 months when she seemed to snap out of this, and would jump on the sofa and my lap for a snuggle, and overall seemed more relaxed, but it went as suddenly as it appeared.
I definitely recommend, and would have my current buns in the house now if I could, but the cat would stress them out too much, and with the two guineas inside anyway I really don't have the room!