Catia V5 (and very soon V6) is one of the most powerful among many CAD/CAM/CAE packages and PLM solutions.
Main scopes of usage are automotive and and aerospace industries.
Catia is de facto standard software for product development in automotive industry, almost everywhere in the world, especially in Europe.
One of most user friendly oriented and coherent environment for design, across all design modules, with clear feedback in graphic window and pleasent appearance.
My personal impressions and experience with Catia, speaking from mechanical designer's point of view:
PROS: - you can do almost everything you can imagine when you master it
- very flexible, you can achieve your goal in different ways
- still impressed even after 7 yrs of knowing it (since v5R5) and working with it...and still learning it
- automation and expandibility through add-ons, scripts, macros, etc are numerous
- works equally well on Intel or AMD machines and both on nVidia and AMD/ATi dedicated graphic cards
CONS: - many things could be achieved in other softwares in a simpler and faster way
- lack of sometimes banal tools/features implemented even in "middle-range" CAD software a good while ago
- almost "legendary" gibberish messages when software is about to crash
- developing in a too diverge directions, seems like Catia's dev team is trying to cover all possible aspects of product design in almost all imaginable industries
- too expensive for small/medium enterprises
Despite of all, it's still one of my favourite CAD packages.
You can take a look at my Catia works and some of the models on this page.