This battery started off incredibly strong, kept my Core2Duo Inspiron E1505 going for a solid 4-5 hours per charge, enough time for me not to need the charger as I studied on campus. This time slowly tapered off over the last year, down to about half an hours worth of charge, and then it died completely just past the year of ownership mark.
By the battery dying, I mean it went from a half hour's worth of charge to not being able to turn on without being plugged in, within two days. Even when it was plugged in, the computer delivered absolutely terrible performance until I simply gave up on the ability to use the battery, and plugged it in without a battery installed at all. This fixed all my performance issues, and I simply have a laptop with no portability now. If you buy a Dell laptop, I would recommend being ready to buy an aftermarket battery within a year of ownership, as their batteries seem absolutely terrible at that mark.