hi, have name changed but have been on MN a while
I received ED from my sister and had my DC last year. She is in fact pregnant herself (so hasn't cause infertility problems for her)
As for difficulty - on the receiving end, no not really. We had compulsory counseling, all together (DP, DBil, Dsis and myself) and then separately as couples too. Dsis had always offered to do it and for me, that was an a amazing offer. For it then to work was just a miracle.
For the person receiving it that would most likely need to go through a process of reflection themselves. Like grieving the ability to have your "own" children with your "own" eggs. This may take time.
Likewise, for your sisters partner/husband - what does he think on the matter? He may not be too comfortable accepting a child that 'isn't his' iyswim? Some people see it that way, that the egg doesn't belong to them but everyone is different.
Now my DC is here, it's not even a subject. DC looks nothing like my sister (all like her dad) and just has similar mannerisms to 'our' side of the family, rather than of me or my sister.
Dsis is on MN, so may well post herself (hence name change!! :o )