Pros: I had a 6-cell battery for the lenovo T420. It used to give only 45 minutes to 60 minutes on a full charge. I need to replace it. I bought the 9-cell from newegg. Fortunately it was on sale too :-). It give me the battery life of somewhere between 6 hours to 11 hours depending on the usage. If I am just browsing with a medium brightness, I get about 10+ hours of life. If I do some heavy processing work, I get some 6-7 hours. Its absolutely amazing.

Cons: I knew when I was getting the 9-cell that it is bigger and heavier but I still don't like it. I wish that we get better technology to reduce the size and weight. (no eggs are reduced for this:-))

Overall Review: Just need to see how long I keep getting this long life.