I did - my daughters were older at placement, and it started as a foster placement. Older one in particular wanted to maintain contact.
First mother was no danger, alcoholic and chaotic, but loved her daughters and supported their placement with me and adoption as being in their best interests.
I have mixed feelings. I think it tore DD1 in two different directions, stability and long-term thinking (get a good education!) with me, excitement and fun and no responsibility from birth mother. As a teenager with LOTS of anger and unresolved issues it was too easy to go back to the excitement and fun (through a teen pregnancy, dropping out of school).
For DD2, removed aged 2 and so with fewer memories, it was fairly straightforward, nice to see her and get lots of hugs but with me nearby for reassurance. Birth mother died when DD2 was 6, so as she has got older and more aware of complexities perhaps the contact would have been more difficult, perhaps not.
On balance I am glad we did (partly because Bm's death was completely unexpected, so we didn't have lots of time to 'see how it goes'). DD1 (aged 20) has worked through a lot of her issues and we now have a close relationship again, she's back education and doing well. Would she if her first mother was around? I think so, but who knows.
So, I think it was worth it now, but if you asked me 3 or 4 years ago you would have got a different answer! And I think that's the case in a lot of adoptions, once your children have reached their late 20s you pretty much know how it turned out, but before that all you have is 'at this point it is XYZ'!
But birth family accepting your role is essential (and of course in turn I respected her role as their first mother, but as the resident parent I set the boundaries).