I am a huge Outlook and Excel fan. Word, not so much. Access is okay, but better than anything else I have access to without resorting to writing SQL myself. I guess I think differently about this stuff partly because I use this stuff 8 hours a day every day for my job, and use the applications to a far greater extent of their capabilities more often than most users.
Outlook is such a boon to my scheduling / meeting / contact / e-mail management. Very easy to set up meeting times and places that work for everyone with the Exchange server. Very easy to set-up To-Do lists, prioritize tasks, set and defer reminders, keep track of partially completed items, make simple group decisions via polls / voting, sharing e-mails & calendars, basic project management stuff, etc. Syncs with almost any portable device too. Basically, I am 10x more productive at work with Outlook than without it.
Excel is one of those killer apps that has basically made number cruching and report generation for millions of analysts efficient, productive, and possible. Besides things like Pivot Tables, vlookups, quick filters, subtotals, counts, conditionals, validation, multiple tabs, sumproducts, paste special functions, time-saving VBA macros, charting, trending & forecasting, and the iterative solver, the way with which you can manipulate spreadsheets is just so quick, efficient, and saves so much time. You can also do some powerful things with its built-in VBA scripting language. Along with Cognos PowerPlay (and to a certain extent Outlook and Access), it has made my career possible and (relatively) enjoyable. Thank you MSFT.
As for which version, I usually prefer Office 2000. I have XP at home, but it manages to buggerise (as Tannin would say) things that shouldn't be buggerised (more so than 2000, which actually does a small enough amount not to be problematic). For example, Outlook XP does not know how to keep a copy of read messages on the server without downloading it again and keeping 2, 3, 4, ... , n copies of your messages... at least on the old pop server I was using. Never tried 2003 or 2007, but can't imagine they made any changes of significance.
As for Office alternatives, I've used various versions of OpenOffice through the years (and whatever it was called before OpenOffice... StarOffice?). Pretty good. The word processor is quite good I find. The spreadsheet doesn't quite compare to Excel in UI efficiency and usability, but it's passable.
I am quite disappointed with Google Docs, however. The UI efficiency and functionality is utter crap; this is especially obvious with the spreadsheet. Smart cell/row/column cut/copy/paste/insert/delete/extend functions are nonexistent, and you have to resort to doing everything manually one function at a time. Everything takes 10x longer than if I were to do it in Excel (and I have used Google Spreadsheets for dozens of hours out of necessity trying to coax it into doing what I wanted it to do).
Besides creating and maintaining the simplest documents which don't incur much editing, the only thing it is useful for IMO is being able to read documents you created with Office anywhere you have Internet access. Very inadequate substitute IMO. If you can't afford Office or simply don't like it (and don't want to bother with WordPerfect, Lotus 1-2-3, or Quattro Pro), OpenOffice is my recommendation. That's what I use at home when I do things for personal use.