Generally, yes. The only time I've had a problem with it is when the her previous relationship was abusive, and she thought they could still be friends. it was a highly unhealthy relationship and it would interfere with ours because I would be constantly concerned that he would try and hurt her again. When he eventually realized she wasn't doing to go back to him, no matter how charming he was, he did become verbally abusive with her and I had to intervene.
Otherwise, I have no problem with it. Sometimes people just don't do well as lovers or as housemates. They may still care for each other and respect each other as friends and I think that's perfectly healthy.