Fellowes 15.4" Wide Laptop/Flat Panel Privacy Filter Model 4800701

Pros: Works like a charm, darkens screen when viewed from the side, making it difficult but not always impossible for onlookers to see what your doing

Cons: dims the screen if you don't look at it in the perfect viewing angle at the right distance.

Other Thoughts: It slightly enlarges your screen in some places so I can see pixels on my screen sometimes

Pros: - Does what it says: prevents from other people spying on what you're doing.
- Easy to take off and clean

Cons: - Gives me eye strain faster
- Reduces visibility
- Smaller text becomes harder to read, especially if you're reading an e-book
- It's dark so you need to turn up the backlight which could waste precious batteries

Other Thoughts: Buy it if you are afraid for your business documents, don't want other people at starbucks know what you are doing and other private stuff. But I would not reccommend it to be always on the screen as it may be of some inconvenience, which I guess is a reasonable tradeoff