This application does what it says, I'll give it that. It has a few more features (and a few less in other areas) than Apple's Calculator.app, but its interface is neither good looking, nor very easy to figure out.

I rate it like this (along with VersionTracker's ratings):

Ease of Use - 3 stars (bad interface - no help documentation) (it would have been worse, but I did like its functionality)
Interface - 2 stars (REALBasic)
Support / Documentation - 4 stars (does have website)
Included Documentation - 1 star (no help documentation)
Features - 4 stars (slightly better and slightly worse than Calendar.app)
Quality / Stability - 5 stars (didn't crash)
Actual Quality - 3 stars (bad interface, but the application does work)
Price - 5 stars (it's free)

I only partially recommend this application, but it was more "Yes" than "No", so I guess I do.

It's a good start...