For me it was a combination of things. For one, I use emacs and a Norwegian keyboard layout, and Apple handily ensures that '\' is only possible to type using both shift, option and 7. Now, since I'm an emacs user, typing meta+\ should mean command+option+shift+7. As if that wasn't bad enough, I never found a way to configure neither Terminal.app nor iTerm2 or whatever it's called such that I could get both option functionality and a meta key (perhaps this has been fixed later? been a couple years), so when ssh-ing I had to use esc, then option+shift+7.

Combine this with how difficult it is to get a real dev environment set up, on debian-based systems you just apt-get install build-essential etc., similarly on Arch Linux, whereas on a Mac it was installing that whole XCode from a CD which included a bunch of stuff I never needed, then waiting for hours for macports to compile gcc etc. (I never understood why macports didn't go with precompiled binaries, mac's are so uniform compared to linuxes it should be _easier_, shouldn't it?). And then waiting for hours every time gcc etc. got an update, thinking "I thought I did this already, what is this, gentoo?" And the annoyance of having to install GNU sed and ensure it was before OS X sed in PATH because OS X sed was horribly slow on certain regexes (I think they had a \1 in them, can't remember), it felt so … inelegant.

And most of the projects I use and like working on just seemed to have better Linux support; of course I could rant about how OS X is a POSIX too and they should support it just as well as Linux, but, well, I chose convenience. For the sake of my fingers and my patience.

It's been a while since I used it, but off the top of my head:

- colors never worked right, you can certainly enable them but themes like solarized are impossible to get working.

- it took forever to open. as in, a terminal on my machine is just a keypress away and it took the terminal on my osx machine a couple seconds to open a window, and even longer to show me a prompt

- somehow they borked mouse input, so clicking the line you want to edit from within a vim session, for example, is a no-go.

- this is a lion problem but terminal interacts with it especially badly, there's no easy way to open a second terminal window. I usually have tons of the things open and it's impossible to manage them properly.

One thing I don't like is you can't completely clear the scrollback, only the visible portion. I often use 'tput reset' when doing new build/test runs and it is nice when the scrollback only contains this time's output.

The few times I had to use it, I could not figure out how to turn off the chrome, though I suppose that is more of a general OSX complaint.

Otherwise, color support at least used to be dreadful. I believe this has been fixed recently though?

I think it still doesn't have proper mouse support though. Seems like a silly thing to have/want, but I find it very nice for resizing/focusing tmux panes/Vim windows, and scrolling in both.

Terminal.app often feels sort of clunky to me. I use iTerm2 instead--being able to split panes is really nice (no, I don't want to use tmux).

The default userland is kind of annoying, in that a lot of utilities are BSD ones and aren't compatible with my imported-from-Linux scripts, aliases, etc., but that's just an install of coreutils away.