This is going to be short; I just want to point out how bad a user
experience this is on OSX.

On windows (and linux) there is ONE default hotkey for cycling through tabs in any UI: Ctrl + Tab

So why does OSX have so many? Here are just a few:

Adium:
Cmd + left/right arrows

Firefox, Chrome:
Cmd + Option + left/right arrows

Safari, Skype, Terminal:
Cmd + Shift + left/right arrows

The worst part about this is that it confuses the text editing options...

If I want Cmd + arrow to go to the beginning or end of the current
line of text and be able to hold shift to select then the Apple
endorsed default (via safari and terminal - e.g. Cmd + Shift + arrows) is already accounted for.

The Current state of things is not good :(

Edit: Things that should be reserved for consistant text editing:

Cmd + Arrow: (go to beginning/end of the current line)

Cmd + Shift + Arrow: (go to beginning/end of current line while selecting)

Opt + Arrow: move one word to the left or right

Opt + Shift + Arrow: move one word to the left or right while selecting

Shift + Arrow: move cursor one char while selecting

As far as I can tell, you can't edit the Safari or terminal hot keys either :(