Probably the first post that has legitimately made me interested in what a Mac may have to offer. That said, the ergonomics of the iPad look haphazard to me.
Suffice to say, I haven't spent a second so far trying to figure something out in OSX that wasn't immediately obvious. Part of this is because I already have a background in other OSes, part of it is because it really is cleanly designed.
Bottom line, if you're a hacker and have been avoiding Macs because of the effort of learning another OS, I can tell you it'll be a piece of cake for you- Take the leap.
I doubt that the hackers who avoid OSX do so because they have to make an effort to learn a new OS!
Admittedly, I still spend most of my time in Terminal and a lot of what I knew transferred immediately (minus the quirks of going from GNU tools to BSD), but even in the GUI parts of the OS there wasn't anything that really surprised me. And once I'd learned the standard keyboard shortcuts I was rather pleased with how completely consistent even third-party applications are about implementing them (a situation which didn't, at the time, exist with most of the GNOME apps I'd been using).
Of course the terminal just feels like home, OSX is a proper *nix and everything works as you'd expect it to. The big difference is that everything else works as you'd expect it too as well. It seems like some sort of dream that I used to spend a whole week setting up a new computer, fiddling with drivers and dependency problems and xorg.conf nonsense.
If you mounted an NFS or Samba share the filesystem driver would 'beachball' the entire operating system if the server ever became unresponsive. There were numerous times where the smbfs driver caused kernel panics too. The only improvement to this offered in 10.3 was a dialog that would popup asking if you wanted to disconnect the share whenever it deemed that the server was unresponsive. Though the 'timeout' that it was using to display this dialog was too conservative. Sometimes it would popup just to disappear right away when it finally get a server response. [Note: these shares were mounted over a LAN, not spanning across the internet or something] The issue hurt me the most when I left a share mounted at home when I closed my PowerBook, only to wakeup the PowerBook at school/work and have OSX require a forced restart because the server was no longer there.
{edit} I know that all platforms have issues, I just get annoyed when people act like they don't.