all this is true if we add "for XCode based development" as a qualifier to "Definitely NOT Apple"
I use an ageing (4yo) 13" macbook as my primary development machine and it works fine. I'm no where near geeky (or whatever term you use) to be even thinking about fiddling with OS internals and I've never hit an OSX bug that bothered me much
And you upgrade the OS on your Macbook regularly? Isn't there a lot of software that drops support for older releases (10.5, 10.6)? Not to mention newer Apple-tested software running slowly on older Macs? I remember Safari and Mail.app just endlessly hanging and giving me the wheel of death on a 2008 iMac and Macbook Pro.