I know this might be difficult thing to ask for, due to the varying requirements and uses of PersonalWiki''''''s, but here's a seed wishlist for the features and characteristics of an Ideal Personal Wiki:

Standard Features:
* Use plaintext wiki pages
* Allow at least basic formatting
* URL and file linking
* Allows export to html - both of the entire wiki or 'subnodes'
* WikiWord auto-completion
* WikiWord Searching
* Incremental Searching
* A rename page function
* Allow for WikiWord aliases
* Software should be ported to PocketPC and Palm
* The Software should also be OpenSource.

Extended Features: (even more wishful)
* Is extendable using a standard scripting language
* support some sort of Tree/Outline view
* also allow some kind of mindmap / flowchart / network diagram view (see sdidesk for an idea) (even better put CamelCase on a network link and it jumps to the page. Also use includes to get diagram and linked text on a page.
* Allow the configuration of the plaintext wiki page extension (for use with less flexible wiki tools)
* Allow for definitions of Interwiki-type standards (this could allow you to use Interwiki syntax to access external applications)
* Allowing for the creation of categories (possibly using folders)
* Allowing the use of filesystem folder structures. This would essentially allow the benefits of a hierarchical structure. (This would probably be terribly difficult to implement - and I'm not sure if it's possible to do without compromising the WikiNature.)
* Some sort of wiki journal functionality - something like EmacsPlannerMode
* Encryption to store passwords and other sensitive data

To Be Perfect:
* Software released under GPL.

---- 
I've long since settled on WikidPad, but very recently have started thinking of TomBoy  -- JaysenNaidoo

''WikidPad is free at the moment. There is a link on their site.'' -- JRoeterd

Yes. Happily, Jason Horman released WikidPad it under his own open source license, similar to BSD license, in June 2005 -- JaysenNaidoo