[griffman]

1) It wasn't a review, it was a First Look as those big words in the title point out. First Looks are just that, a quick look at the major new features of an upgrade, or the maor features of a new release. If it had been an actual review, you would have seen a mouse rating, pros, cons, and other such information, along with the big word "Review" in the title. There was a big hint at the end of the First Look, too, in this line: "Well have more definitive thoughts about Numbers and its features in Macworlds full review of the application."
Said review will be published shortly, and it will discuss both speed and Excel migration. I'm also working on a more-detailed piece that looks at all the various spreadsheet apps on the Mac, though I don't know when that will be done.
2) Please don't question my qualifications without knowing my background. For 15+ years, I made my living using Excel. Macros, complex formulas, monster worksheets with over 100 tabs, database usage, custom menus. You name it, I was responsible for it. I used Excel at Apple, IBM, and a small company that grew 20-fold in revenue and earnings during my tenure. I have a BS in Finance and an MBA with a Finance concentration, during the earning of which I served as a Finance teaching assistant. I feel well qualified to write about Numbers, thank you very much.
3) Numbers isn't targeted at Excel switchers, at least not those building much beyond simple spreadsheets. Just like Pages isn't targeted at hard-core Word users. (Keynote is the exception of the trio, as it does a very good job at competing with PowerPoint.) For many, many users, Numbers will impress with its feature set, and they'll never complain about any performance issues because their sheets will be simpler than yours.
4) Keep in mind that Numbers costs $26.33 (of a $79 suite) and has existed for about a week. Excel costs $100 (of a $400 suite) and has been around forever.
-rob.

[aafuss]

I use mutliple sheets and tables in Numbers-at the price, who is likely need to a separate database? Only FM users, I think.

Seems to be not slow, even on my 1.5GHz Mac mini (Core Solo CPU).

[aafuss]

I am longtime MS Works-and Numbers is way better than the MS Works spreadsheet.

[ecotrend]

I've been using Numbers for just a few days, but I am very impressed. It is worth buying iWork for this application alone. I find the canvas layout options are worth their weight in gold.
I have to use spreadsheets regularly but am not a very 'deep' user of them. I can't see myself using Excel for anything I do at the moment.
Pages is also much improved - but then I guess like most people I actually don't produce many paper-based documents any more.
Keynote is just superb.