I just recently started using Numbers, the Excel replacement for Apple. While I do have a few nits, my overall impression is that it offers a pretty decent mix of both simplicity and power.
One of the power points is that a work space can contain several sheets and text spaces which you can place down as if you were working in a Pages document. I know you can setup all of this in Excel but the way it is working with Numbers is like you were setting all of this up in Word but without as much fiddling about.
I did reach a pain point today when I tried to import a CSV data set. No matter what I tried it all ended up in a single column. Since the other option mentioned was tab delimited fields I sucked the file into vi and a quick s/,/\t/g later and had a test file. Numbers parsed that file as expected.
I don't really care for openoffice as it just feels klunky when stacked up against MS-Office. So I decided when I switched that I would buy a copy of MS-Office for the Mac. That was more than a year ago and Office still sits in it's shrink wrapped container. I've Neo installed but I rarely use it. Instead I've found that iWorks Pages, OmniGaffle and now Numbers have more than filled the need.