I was Palm guy and not Blackberry, so I went from a Palm Treo to webOS. After that though, I went to iPhone. I considered Windows Phone though. The tiles and text orientation were so amazing. I am, however, glad that I never went down that road, not just because Windows Phone died, but also seeing what has happened to Windows more recently.

I was seriously interested in PenPoint, but it was too early for tablet PCs to succeed. Handwriting recognition was nowhere near mature enough yet and unfortunately that became the main issue in that niche. Even Apple pretty much failed with the Newton because of it.

But PenPoint had a lovely UI and, if memory serves, an API much like Apple's Objective C.

Microsoft had a hand in killing PenPoint, just as they did with BeOs. Jerry Kaplan told the story in his book "Startup".