By far the best for students of polytechnic and generally positive sciences. It is worth the price difference from the 991ex plus 2nd edition. (Faster, much better screen, menu)

An essential tool especially for students of the exact sciences.

It takes a little getting used to if you were using an older model since there have been some changes.

I finally consider the rounded buttons more convenient than the older square ones.

One downside is that it does not have any kind of rubber on the back to stabilize it, especially when placed on smooth surfaces.