There were a number of similar batteries offered - this was one of the more expensive ones. But I bought one, because i need a new battery. With Paypal, I have 30 day to return. Just now, I need a battery to last 8 hours.
Well, I boughtit and can recommend it. But take time to search, there are some that sell separate charges for the battery. The problem is that the N900 will only charge to 1290mA and will then stop and enter maintenance charge. You can then remove it, and plug it in - or charge it while the phone is off. But the hardware will also halt the charge.
Someone should write a patch that change the battery capacity - it is not that difficult algorithm. The battery technology has made good progress since the N900 was designed, and 4000mA will soon be available. The charger is software, its described here. My Mac has a similar chip fitted in the battery which makes it impossible to recover a deflated battery.
So, if you buy the battery you have to buy a separate charger to get it charged above 1280mA... But the phone lasts at least 50% longer than on the old battery.
And here it says that the batteries develop and improve, a factor of 10 times should be within reach. Now my N900 has lasted 4 years and runs application that Nokia never considered possible. But the charger, the software that drives the charging of the battery has not been changed - and changed battery needs a charger for more than 1280mA, according to the thread, one designed for 10 000mA. You need a charger that can "drain" and try to recover, change charge bursts. This is one benefit with the N900, access to open source code..