If you want to change your hotkeys, consider using Dorando's keyconfig extension -- here's some more info on the extension. Be sure to read the first post (by Dorando) in that link very carefully, and consider clicking on the 'Example custom keys' link as well -- it's right above the Changes: section of the first post. It's an awesome wealth of possible keys.
For example, I added a new key called 'Next tab,' and pasted in this code:
gBrowser.mTabContainer.advanceSelectedTab(1);
I then assigned the Command-Shift-Right Arrow hotkey to it. Then, of course, I added a 'Previous Tab' key by changing the 1 to a -1, and assigned it to Command-Shift-Left Arrow. Hope this is helpful for all your Firefox key mapping needs! BTW, I am grateful to the Firefox user community for providing such excellent online support and even live support via IRC.
[robg adds: At least in the case of Web Search, you can also reassign the shortcut key using the Keyboard & Mouse System Preferences panel. Make sure Firefox isn't running, and thn hit the Plus sign in the Keyboard Shortcuts tab, find Firefox using the 'Other...' option, and then enter Web Search as the command to be assigned. Enter your desired shortcut (Command-Option-F), and then click OK. Next time you launch Firefox, you'll have your Safari-like web search shortcut. This won't work for Previous and Next Tab, though, as those shortcuts do not have corresponding entries in the menus (at least not that I can find).]

