Xp and i have been living this way, as roommates, for many months. He is moving out in about 2 months though. When this arrangement seems to be working (ie. we're not fighting) we've entertained continuing on like this until dd is older, but we have acknowledged that we can't really move on emotionally while we're doing this, and we'll run the risk of turning a fairly amicable situation into an animus one.
Some of the ways that it works/is good:
While a lot of the same issues come up (we are, after all, the same people), i definitley have an easier time letting things go b/c there's an end in sight-- everything isn't compounded by me trying to figure out ways to cope for a lifetime with him as my partner. Instead i can focus on trying to appreciate things i like about him as a friend and father, and look forward to the opportunity to meet someone with whom I'm truly compatible.
Dd still gets to see mama and daddy every morning, even if daddy sleeps in a separate room.(Having separate rooms has been crucial in making this arrangement work — I started to feel much better once we created that space). The hardest thing for me to accept about the failure of this relationship is that we will have to split dd. I will have a home, and he will have a home, but she won't have a stable home... she'll be shuffling back and forth. It's not fair to her. If you're living together as platonic housemates, that won't be your kids reality.
We're still splitting everything 50/50 — bills, groceries, rent, etc.
Some of the ways that it doesn't work:
Even though we've clearly established we're not together, this is a big fat gray area. When we're getting along, I sometimes find myself thinking "he's not so bad, maybe this could work." Of course, then he'll do or say something where I'm like "Oof, yeah.... not so much." But then I still have to share space with him. It's like you can let things go more because you're not attached to them in the same way, but they are still the same person with the same annoying/hurtful/infuriating behaviors, and you have to share space with them.
It has been so long since I've been intimate with someone that I'm starting to go a little crazy. But there's zero chance of me meeting/dating/talking to with anyone while I'm living with XP. He even randomly met my chiropractor the other day — who happens to be an attractive but very attached male — and referred to me as his "girlfriend," because he "couldn't think of a better word." Serious jealousy issues.
He has started acting sort of... competitive. Like if she starts to cry, she may be crying for me but he won't hand her over. Or he'll get mad that I let her crawl into bed with me. I've always done 98% of the parenting, day and night. But now, it's like he still makes me to do all the work, but acts like I'm doing it to edge him out. I'm sure this will get worse once he moves out, b/c dd will continue to live with me b/c she's so young still, but when he's not living here, he'll have to make a specific effort to spend time with his daughter, and that'll be a good thing. and i may have to do more b/c he's not here, but at least i won't be working around him. which is also a good thing.
I don't know, I guess that's all I got. I think whether this will work for you will depend on your unique dynamic with your stbx, why you guys are splitting, the age of your kids, all of it. I read somewhere that if you can live together and not fight, you should, for the kids. But if you can't get along, it's better for the kids if you live separatley. Me and xp hardly fight these days... but we're still not happy, not fulfilled, not the people we could be if we weren't living together. And I don't think that's good for dd either.
Hope this helped some. Good luck!