Video Demo of completion in use: tripledoubleyou.subtlegradient.com/stuff/blog/MooTools%20Completion %20Demo/MooTools%20Completion%20Demo-iPhone.m4v
The final completion list will have better snippets and will show a tooltip once you select one.
Mockup for how it could look awesomer: http://tripledoubleyou.subtlegradient.com/i/tm/TM_D2_popup_mocks2-8.png
— thomas Aylott @ subtleGradient