I've got 2 sets of Inca 2500mAh's that I've had for 2 years and they are still holding charge and working well.

The best set I have are Panasonic 2500mAh's I only have 4 of these, and can't seem to find them again, but they are unstoppable! I've left them fully charged for a month or more, grabbed the flash and still rattled of 100+ flash photos with no slow down in recycle times.

I've got Sony 2700mAh's in my D300 grip and on the weekend took 3000 photos over 2 days with heaps of reviewing and the battery meter still hasn't dropped to half yet!

I've not used the Sony's in a flash yet, but given their performance in the camera I would say they are going to be great. They retail for about $40-45 for 4.