The hunt for a nice and cheap mockup tool.

Time has come for my pet project to assume a form of a software program. And this marvel will have a user interface. Being a User Experience professional I can't leave the interface to just come to be by anyone who happens to be in charge of the IDE churning out the code. There must be a propper process. The hunt for a tool, that will help me create the mockups has begun.

FYI
My tool of choice would be Visio 2007 (Professional if I could have it), because that is what I use at work. Just a few highlights for those, that aren't so familiar with it. Visio contains the following features, that make my work much easier:

• Layered pages (1 foreground page, many layered backgrounds)
• Ability to create 'interactive' prototypes (any object can be a hyperlink to another page in the file)
• Speed of creation - fast duplication (CRTL+Mouse Drag duplicates, F4 repeats last copy)
• PDF Export, that still maintains the hyperlinks
• Lots of available object libraries (Software design stencils are part of the Professional version only, but some alternatives can be had for free on the web)
  

The Criteria
Currently there are a few program I intend to evaluate. The criteria for inclusion are roughly these:

• Ease of use (should not get in the way of my intentions at the very least)
• Fits ony my netbook screen (1024x576)
  
• Overall appeal (I hate bloated toolbars, ugly icons and other ugliness)
  
• Must Features (what must be in)
• Can export interactive prototypes
• Ability to create custom components (I know I need this)
• Basic component library available (text inputs, combo boxes, tabs, menus and such)
• Optional Features
• Collaboration
• Task Tracking
• Anything else, that helps me reach my goal faster
  

The Contenders

A scan of the internet has yielded many results and these are the happy few:

• iPlotz
• Balsamiq Mockups
• Pencil

And these were disregarded due to different reasons:

• Axure RP Pro ($539 for a hobby project?)
• gliffy.com (too slow, not a fan of 'Loading', does not fit the small screen)
• Visio (the price for the Standard Edition is somewhat less than for Axure, but still way too high)
  

Hopefully there will be time for any wireframes so I can test the tools. Two kids and a busy personal life slow everything else to a crawl.