I've been reluctant to use anything but Excel for a long time... the last vestige of being a Windows user, I suppose (even though I haven't been one for over 1.5 years.)
This thread got me thinking though... I recently began using Pages for all of my assignments (college😉 it looks better on my monitor and isn't crapped up with all kinds of menus and toolbars and whatnot (Inspector rules!) I use Keynote for class presentations (even though they have to be converted to PPT so I can use them on my professors' computers, and it ruins the beauty of it all.)
I created a spreadsheet in Excel about a year ago; I was spending way too much of my loans too soon and not realizing it, which caused some horrible money problems. Tonight, I opened up Pages, created a table, and got it all set up. It looks much nicer than Excel, and was so much easier to use (especially my equations; very easy to set up.) Plus, my iMac has the stock 512MB of RAM; Rosetta is impressive and all, but my computer takes some time to open PPC apps, and sometimes takes too long to modify things once opened.
I suppose it probably depends on your needs; if you've got to swap files with other people all the time, or have some heavy-duty uses, Excel or OpenOffice/NeoOffice would probably be better. If it's for personal things, I'd just use Pages. Truly great (and I was a real Pages skeptic up until about 6 weeks ago.)