Tools --> Options screen isn't quite set up the same way
True, although I prefer OOo's version (just a personal preference, most likely). And I particularly like Format -> Page instead of File -> Page Setup (in 2003) or Round Orby Thing -> Prepare (if you're getting rid of menus in favor of ribbons, why keep one unlabeled menu?!?).
Doing cell borders is a pain in OOo but very easy in Excel.
Really? I use both (Office 2007 and OOo 3.2) on a daily basis, and I've not noticed any difference in border management ease of use. What I actually notice more is cell shading - 2007 keeps my color selection when I click on another cell, making shading disjointed cells easier than in OOo. 2007 also has better style management IMHO, although bizarrely they don't use the same palate as 2003, which makes switching between them an exercise in frustration (some of the conference rooms at work are still at 2003).
The big purple lightbulb box
Die, die, die! (I turned it off, of course.)
Asking me every single time
You must be right-clicking to Delete Contents..., or pressing the Delete key? The purpose of that is to ask you every single time what to delete (it's a feature). Try hitting the key on your keyboard marked "Backspace". It just deletes the contents, no dialogs. I hadn't really noticed this before - I've always used Backspace to clear a cell (on 2003, 2007 and OOo), and I've always used a right-click menu to bring up a dialog. Interesting.
Really, unless you're a math power user who needs obscure functions or Excel plugins, the differences between the two seem to come down to preferences. I like the customization of OOo more than 2007 (which has little - 2003's was better than either). I LOVE the consistency across the suite in OOo, which is lacking in 2007 and 2003. Overall, I feel comparably productive in 2003 or OOo, and a bit stymied in 2007 because of the ribbon - but I've only been using the ribbon 18 months. Fans keep telling me I'll get used to it...