SimpleDruidBar 

As the name implies, this version is much simpler, and as a result is more efficient. The original is about 120KB large, while this version is roughly 28KB. This is due to it having all manner of extra features (such as custom bar graphics and color, special keybindings to switch forms, automatic chat messages when shifting, and a GUI configuration frame), all of which are nice, but not necessary. It also uses some outdated detections for, and calculations of, mana regeneration, resulting in accuracy falling below 95% if you spend a long time in a form. This version was written with utmost accuracy and efficiency in mind, and although it is not yet possible for any addon to approximate your mana with >99% accuracy, this can come pretty close over any duration. In the expansion, it will be possible to garner 100% accuracy at all times, and I already have the code to do so written.

Anyway, I mostly just wrote this addon for myself, and uploaded it in case anyone else wanted a more compactly designed edition of the DruidBar concept.

Just uploaded a fixed version. The GetManaRegen function has indeed been removed on the live patch, but ought to be back when the expansion is released.