I have been using Sun's Star Office Suite as an alternative to Microsoft Excel and Microsoft Office for about three years now, and I can tell you that it is particularly strong in the arena of being able to read documents from Microsoft Office. When I first started using it, it was downloadable for free. Now it is still downloadable but costs about $76 if you decide to buy it. Still, that's a very good price for such robust multi-purpose stable basic-programs software.
I have never had a single problem being able to read a document someone sent to me or being able to export a document to someone who insisted on a Microsoft Office-compatible format. Most of the time I do not bother to tell them that I do not any longer have MS Office Loaded on my computer. This suite is available from Sun.com Drawbacks, it's a bit slow in Windows, it takes getting-used-to. I guess there is this or that drawback to this or that app within the suite. But I don't really care, as who uses 99% of the details of these apps?
When I first got it and had a spreadsheet project, I had to keep Excel loaded for one or two functions that I couldn't find in StarOffice. Otherwise I devised my stock index research here:
using StarOffice Spreadsheet entirely. Sun is doing to MS Office what MS Explorer did to Netscape Browser (giving away an equivalent product and ruining their market share or potential to make profits). They are doing to MS Office what MS Word did to Wordperfect: slowly chipping away at what was once assumed to be an insurmountable position.
Oh yeah, it has a browser that works quite nicely (which makes sense when one considers Sun's experience with connectivity this makes sense), but I don't use it much.
It is not perfect. But it can pretty much do everything you'd expect from an Office Suite. I don't know anything about how its db qualities are. Remember: it is Sun, so it is not fly-by-night.