Psion, the grand-daddy of Symbian, created the PDA market and pioneered the idea that an electronic organiser can be a bit more than the love child of a calculator and a stopwatch.
But while anybody with any sense will tell you that the Psion based organisers were (and indeed are) advanced beyond their years and certainly even today show how a mobile OS should be built (just look at how the Notebook's specs have had to change just to accomodate the new bloatware OS from Microsoft), most of these same sensible people will tell you that from a business point of view, Psion wasn't going to get far in a market that was flooded with Palm devices and the terribly flaky, but incredibly pretty PocketPC.
The old Netbook had its fans, but it wasn't going to go anywhere as far as Psion, as a business, was concerned. It's best bet was to try and weigh up its options and it chose to go for Windows CE .NET in an attempt to woo corporate users who.
Is this bad news for Symbian?
In my opinion, certainly not!
Symbian has shown that it has now grown into a platform ideal for the Smartphone, in fact I think it should be true to say that Symbian is to the Smartphone what Windows is to the Desktop - a de facto standard with which normal people are comfortable (the main difference being that Symbian is actually quite good).
As far as the industry is concerned, Symbian is a damn good Smartphone OS. Sure, it can run PDAs, but why bother when that market is contracting anyway and World+Dog is 'converging' (sorry Register

It could have been used in the Netbook (as it was), but why bother any more with that anyway? It's hardly a mass market device and at least Psion can rest assured that with the 'upped' spec and a Microsoft OS, it can hit the ground running (or crawling, depending on how you view Microsoft software).
Saying that Symbian is dead because of this is stupid and shows an incredible short-sightedness as well as a complete misunderstanding of the market.
British Airways don't make cars, so does seeing British Airways purchase a Ford pool-car mean that British Airways has no faith in their aircraft?
Symbian is here to stay and this decision of Psion's to move to a Microsoft based OS has absolutely no effect at all on the reliability, preception or future of Symbian.
In fact, this decision shows the maturity of Symbian as an OS; that it's developers knows where its strengths are, they know what it can do and are quite secure in their minds (ie, they don't feel threatened) with the idea that another device (by a founding organisation) could run a different OS for a different class of device.
So chill, the future's still bright!