There could be a number of reasons to turn away a solution. It's not always about stability of the platform. Could be the software packages didn't deliver as advertised (read: software is not the same as the platform). I think it's important to note the distinction.

Windows Mobile (WM5) and PalmOS apparently are going in opposite directions in terms of perceived quality and stability. There has been growing criticism of the PALM OS (particularly version 5, Garnet, I think it's called). When you put that together with the fact that Palm has decided to partner with Microsoft, it's hard not to come to some conclusion that Palm has somewhat conceded the platform of the immediate future leans towards Windows Mobile. At the very least they are going through this trouble because they believe WM5 is somewhat of a growth opporunity.

Palm used to rule with simplicity and rock-solid stability but it appears they succumbed to the pressure to be all things to all geeks and have overloaded the system with a variety of nuts and bolts. My theory is Windows Mobile started out this way and perhaps were ahead of Palm, through 5+ iterations, of getting all of the features into a more stable platform over time. Palm has tried to do this in approximately two years in catch up mode. Apparently that isn't the best way to go about it.