Franciso had a great idea there, something I'm going to definitely try before I move in with whoever I move in with next. Always live with someone before getting married, and always vacation with someone before living with them.
As far as it goes Hellboy, there are positives and negatives of living together. I've been in one live-in relationship where the girl was wonderful, but living together killed the passion since I ended up seeing her in crappy home clothes all the time and just started to find her non-sexual after a while. Ended up seeing her bad sides, which werent major, but definitely enough to make me reconsider the future of the relationship (which is why its best to live with somenoe before marrying them, btw).
On the flip side, another girl I lived with only because her place got ****ed up, and she moved in for a month. I realized she spent most of her time naked and was much more fun than when we were just dating. It was an incredible time, causing the relationship to last much longer than I had originally thought it would. It also let me see her weak sides, etc.
At the end of the day, moving in together really helps you cement what the future might hold, and sometimes that could kill a relationship, and other times it could shove you into one-i-tis (assuming thats a bad thing). Obviously there are constraints on your freedom too, such as not having other girls, possibly changing your routine somewhat, etc etc.
Not a decision to jump into, and perhaps one left for a relationship that has lasted longer, but hey, only you know how intense your relationship is.
And again: Solid post Francisco.