I noticed today that my 17" MacBook Pro, after two years and change, just hit 300 charge cycles. The reported health is still 94%. I haven't done a true end to end drain of the battery in awhile, but I have to guess that it's still doing about 6 to 7 hours of usable life. At the conference in Vegas last month, I still had plenty of charge when I dropped it off in the evening before dinner.
Keep in mind that I changed out the hard drive for an SSD recently, which undoubtedly gives it a boost. The original drive is still in there, sitting in the DVD bay, but it only spins up if I'm using it. I mostly just have photos on there, so unless I use aperture or the screen saver fires up, it's not turning.
For comparison's sake, my original, first Intel 15" model, went through two batteries in about three years. I replaced the first one I think after 250-ish charge cycles, with battery health down in the 70% range, lasting around three hours. So it appears that Apple has more or less delivered on its promise of adaptive charging and such.
Granted, I can't tell you if my results are typical. My friend Aaron from work has a 15", maybe a little newer than mine, and he gets crappy battery life with fewer cycles. This implies different charging habits. For the most part, I would drain mine nearly to zero before recharging, though I did from time to time go less. Interestingly, Apple says not to do that, except once in awhile to let it calibrate its full range. They describe an ideal scenario as someone who uses it on their bus commute, and plugs in during the day. Also, when you run it in Boot Camp mode with Windows, all bets are off, since I think the OS has a lot to do with maintaining battery health.
It's kind of interesting to think about how far batteries have come in the last few years. My last iPhone (a 3GS) easily went two, sometimes three days without a recharge, though I never used push e-mail. My Samsung Focus is easily going two days, with push e-mail on, since the software update. I just got the iPad 2, but it doesn't look like that will need very frequent charging. My camera batteries go about 400 shots before needing a charge, with lots of idle time. The tiny camera doesn't go as long, but that's because of all of the mechanical opening and closing of the lens and flash every time you turn it on.
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