I would say it's dependent on how the relationship will be, if they are fulfilling the role of an absent parent, then really loving that child becomes important, especially if there are further kids in the mix, but if the child has a father who's still actively involved in their child's life and shows them the love that a father usually would, then its not quite so important.
I grew up in a household where my stepfather was allowed to demonstrate that he didn't like me very much, certainly didn't love me. He was called Dad because my mum didn't want the embarrassment of explaining that I wasn't his, and certainly didn't want to explain that 2 of her other children were also not his.
We were treated differently. Hugely differently to his own child. Our youngest sibling was definitely cherished and cared for, whilst I was treated as an inconvenience. When my siblings found out that he wasn't their biological father, their response was, we always thought that might be the case, you treated us more like you treated nowayout than you treated "xxxx"
I personally couldn't have settled down with a man who didn't love my daughter because of that. DH has a lot of real negatives, but the relationship he shares with DD is beautiful. He loves her and for all the years we suffered infertility he always said that he was happy with the family set up we had. He has a lovely daughter to dote on.
Might have been vastly different if DDs dad was in the picture though.