I purchased this battery for my x60s notebook to interchange with my 4 cell battery.
This 8 cell battery does last long. When I have wireless network on, and a firefox browser, a word processor, a notepad and a messenger program(s) open, at battery's 76% it says it will last another 6 hours 45 minutes. It's not this long when I have programming environments running though.
The cons:
1. A bit heavy. It is 8 cells, and it's bound to be heavy, and I knew that before I bought it but still... You will really feel the difference when carrying an x60s with the new battery. If you don't mind the extra weight then this is no problem.
2. Adds 2,5cm to the back of the x60s notebook. Be sure to check if your current notebook case can fit the extra length. I didn't and had to buy a new case.
Tip: make use of the advanced battery maintenance feature. Set the battery to start charging when your battery reaches 40% and stop at 98% (for example). This way when you have a short meeting or have used your battery for only a while and you still have 80% (for example) your computer will not charge it. Your battery does have limited charge life. I didn't know this at first and thus my 4 cell battery only has 60% of its original capacity (after only 1 year 3 months).