LibQTip is designed replace GameTooltip - but with added functionality, such as multiple columns - from a minimalist design perspective.

Features

Ability to display and handle multiple tooltips at the same time,
Unlimited number of columns and lines,
Column default and per cell justification,
Tooltip default and per cell font setting,
Colspans,
Possibility to add custom cells,
Optional scrollbar,
Optional scripts for lines, columns, or cells,
Optional automatic hiding,
Frames and tables recycling to reduce resource footprint.

Caveats

Look here for information on embedding the latest beta/release.

In order to achieve effective frame recycling, tooltips must be released. Holding a tooltip leads to the creation of a full set of frames for every AddOn which does not follow this practice. Moreover, releasing a tooltip has a very little overhead compared to its benefits.

Known issues

Alignment may be altered when using :SetScale after filling the tooltip.

Documentation

Getting started guide.
How to add custom cells.
API reference.
Official Forum.

LibQTip-1.0