Psions were wildly successful and this recent article should help clear up why they ultimately failed (mainly due to poor management who lacked the nerve to innovate, among other reasons including the sale of some operating system software to Nokia...)

As far as PIM is concerned, I can understand to an extent why Nokia don't want to provide it (is it because it competes with the E-series phones?) but if PIM is a barrier to customers buying the Internet Tablet, doesn't it become a pointless debate? Shouldn't Nokia be offering customers what they want rather than telling customers how it should be?

(Lack of) PIM is always mentioned in reviews of Nokia Internet Tablets, and it's a question that never fails to be asked when I show my tablet to other people - their reaction when I say there is no supported PIM/sync functionality is never positive, and generally they rapidly lose interest because they already have a PIM device and don't see the need to carry yet another device in addition to their PIM.

Look at Palm with the Foleo, as they seem to "get it". While I don't necessarily agree with the form factor of this device (too big) I have to admit that it offers compelling functionality that could also be offered on the Internet Tablets.

In a few years instead of asking why did Psion fail, maybe we will be asking why did Nokia (Internet Tablets) fail... and I hope the answer isn't "because they didn't offer PIM".