I think it all depends on the size and layout of your house - we have a small two bed flat + small balcony, so we have toys in the lounge room (lounge, kitchen, dining is open plan) - DD could play in her room and does sometimes, but I would rather be able to see her rather than interrupt what I am doing in kitchen or on computer to check on her - and in the lounge I can always see her, and she can see me. We are pretty restrictive on toys though because of the size of the flat. I enjoy playing with them, and rearranging them myself and if were in DD's room couldn't do that when she is in bed - I see myself as some sort of toy fairy so often the next day a different selection of toys will be accessible.

I have a very high tolerance of mess and disorder though (which from reading these forums seems uncommon) so toys in the lounge room don't bother me in the slightest, and even if had more space things would probably be the same. I don't remember playing in my room very much until I was maybe 8 or 9 and always preferred to be playing downstairs where other people were.