I are a bit of a cheapskate and when I wanted more features than I get with the Works spreadsheet on the home computer, I decided to try the OpenOffice.org Productivity Suite. OO has a distinct price advantage (free) over competing products.
I've only been running it a few weeks, but am happy so far.
I've mostly used Calc, the spreadsheet. Commands, buttons, and features are very similar to Excel and I haven't had any trouble reading or saving to .xls format. The OpenOffice spreadsheet has a macro language, but the documentation says it isn't directly compatible with Microsoft's VBA because the object structure is different although the basic code language is supposed to be very similar. I haven't tried writing any macros or importing any from files at work, so can't comment on the differences. If the OpenOffice documentation is correct, importing an Excel macro would simply (or maybe not so simply) require rewrite of the object references. It's been years since I've written VBA code, so not too worried about the compatibility.
I did try Writer and when I opened an MS Word document, not all the formating came through, but, like the spreadsheet, the user interface and features looked very similar to Microsoft products. Since I have Word on the home machine, I doubt I'll use OO's word processor much.
I haven't tried Impress, Draw or Base (the presentation, drawing and database apps) yet, so can't comment on how thy work.
If you're considering upgrading or buying MS Office or another suite, recommend trying OpenOffice first.
[Obligatory investment related reference for CAPS]
Money saved on software spends just as well as money earned in the stock market.
Any one else have experience with OpenOffice they'd like to share?