Reading this page at Wegmans where I bought broccolini this weekend - they were being demonstrated - I made them at home last night. They were delicious.
I note in the article it says that broccoletti is trademarked broccolini. I have bought broccolini in the past, but I note that it was always very small in length and diameter; whereas this broccoletti I bought was large, but not as large as a broccoli stem.
As it was larger than broccolini, I was concerned that it might not be as tender - but it is sooo tender. Today I took a bite of left-over-in-the-refrigerator-last night. It was so delicious that one could easily serve cold.