My 13' macbook pro (mid 09) has been fine with snow leopard... However, after I upgraded to OS X Lion, lion started to suck the battery of my macbook quickly, generate a lot of heat, increase fan speed, and most importantly slow down my macbook pro, although it was used for normal internet browsing. I'm so disappointed with Lion. If this situation lasts, I will downgrade my macbook back to snow leopard. Latest Update: My macbook is back to normal. The initial dropped performance is possibly due to spotlight indexing that causes me panic, as others mentioned ><. All new Lion users, this is normal. No worry. But, I feel the startup and the login is slower than before.