It's already a 17" machine - i.e. bloody huge. Seriously, is a removable battery going to make that much difference? I expect their thinking is that no-one is actually going to travel with it (which I can understand : I've got a laptop with a 12" screen because it's portable), but it's nice to have the option.
Also, if you're regularly using a laptop on mains it's a good idea to be able to remove the battery, as I believe leaving the battery in usually initiates a continual slight discharge/charge cycle..
$200 is hideously expensive for a replacement battery especially if you believe the comments above about batteries only being covered for 90 days (IBM warranty for a year. I'm sure others will too).
I would also be prepared to bet that replacing the battery yourself invalidates the laptop warranty - it's not a matter of being scared to wield a screwdriver, it's a matter of maintaining your investment in a piece of kit (laptops) which tends to be less reliable and more expensive to fix than other kit (desktops). The target market can undoubtedly afford it but it still feels like a rip off of a captive market.
A Mac Pro is a high price regardless of the value for money it offers (which considering the workstation chipset, FBDIMMs, water cooling and 5 OS X licenses is not unreasonable). I'm not denying its value, but the expense will deter people. Without wishing to be offensive 'expensive' is entirely appropriate if you use the dictionary definition.
I'm not interested in integrated products from any supplier. Not Apple, Dell, HP, IBM etc. I already have excellent display devices and input devices. I don't want another, especially when most of them contain laptop grade components. I also don't particularly care about appearance - it's a box, and it sits under the desk.
I already run several Unixes; they're not OS X - which is practically the only reason to buy a mac.