L.H.
I used the Nuby cup, too, and my daughter didn't even notice (we had Platex bottles before). I spent weeks worried about the transition and she barely noticed a difference. I credit that to the soft rubber spout, which is very much like a nipple on a bottle. I would highly recommend them again, even more so after reading all the great comments here that echoed my good luck with them!
I just bought the Born-free trainer cups online for my son after reading on Amazon.com that they had the same ease in transition ~ and they are certified to be BPA free (my son is only 7.5 months so since I'll still have to heat the liquid in them, this was a concern, unlike my daughter who I transitioned at age one with cold milk). I have yet to receive them as they are all back-ordered, so I can't vouch for them just yet :)
L.