Adobe Reader is UI is simple and intuitive. Classic tools (text selection, zoom, snapshots, find, etc.) can be accessed from the top navigation menu and buttons. The latest version also includes advanced Tools (create, export, send and store options), Sign and Comment features. You can share iterations, comments and signatures by email or using the Adobe SendNow service.
Adobe Reader XI is the safest version Adobe have released. This is mainly due the new Protected Mode which loads potentially hazardous items and code in a sandboxed area, isolated from the rest of your system.
There have been some criticisms over Adobe Readers speed compared to other lightweight PDF readers. It is true; Adobe Reader does have more plugins and extensions than most PDF readers which can slow operation. That being said the difference for the average user is negligible and those add-ons can be disabled if they are not required. In terms of general operation, Adobe Reader renders documents with high detail and true colour reproduction quickly. Later editions have also had work done to improve Adobe Reader’s impact on memory usage so you should find multitasking takes less strain on your system.