well of course the first smartphones of any note *were* PalmOS smartphones, starting with the Qualcomms, and the Kyocera. Then the Samsung (i300, i500, i550) and Handspring, and Treos. PalmOS ruled the early smartphone market but then it simply stagnated (and was too underpowered and under-architected to support the explosion of hardware capabilities). And of course webOS was way too late.

But I well remember being very happy with my PalmOS Samsung i500 for a good while...