Having slept on it overnight, I think I've asked the wrong question. Perhaps I should have asked: "Is Tiger likely to change my perception of the Mac?"
I'm still planning to sell this iBook and get an XP laptop. When I got the iBook - it was my first Mac - I was promised a life-changing experience. I soon found otherwise, and a year later my view hasn't changed.
This is not a 'grass is greener' case - I'm using XP and Windows Server 2003 at work and the Mac is for home use. At home I still have my 6 year old PC laptop, upgraded to XP, and it actually feels faster and easier to use than the Mac, but it's now faulty (prone to random switch-off, screen colour has changed) and isn't worth repairing, doesn't have wifi, is bulkier etc.
This thread isn't the place to go into why I haven't 'taken' to Mac/OSX.
But it's partly the OS experience (e.g. Expose makes me nauseous, the bin darts about unpredictably when I try to drag things to it, you can't empty the trash selectively, you can't maximise windows fully or make them wider except at one corner, I can't get used to the menus always being at the top, the Dock is rarely needed except for starting programs three or four times a session, minimised windows aren't easily identifiable on it, the list goes on).
It's partly the hardware (the trackpad is prone to being triggered accidentally by my palm as I type but the Apple shop have told me it working to spec and I will be charged to replace it, the physical keyboard layout is American even though it is supposedly a British unit with UK mapping - the list goes on).
And it's partly being out on a limb (too many web sites don't support Safari or Firefox, much of the latest must-have software isn't available for the Mac, people don't expect their users to have Macs, accessories are harder to find and more expensive - the list goes on).
Is spending money on upgrading Tiger likely to make me change my mind? Probably not, although it would be nice for me to say 'yes, I've tried it'.
But is it likely to make it more appealing to a buyer of my iBook? Thinking about it overnight, I've answered my own question. Most of the things in OSX that don't appeal to me are central to what Mac enthusiasts like, so it's unlikely Tiger will be more configurable.
The cost of upgrading is probably the difference between a cheaper PC laptop and an upmarket one (e.g. Sony Vaio) so I might as well leave Panther on this Mac and spend the money on a better XP laptop.