Welcome to Mac
Quicksilver. Even if I'm trying to wean myself off it until it's fully compatible with Snow Leopard (might already be, mind you- hope to find out soon
)
I add myself to the line in praise given by
ShortNCuddlyAm for Twitterrific. Lot of customisation AND still you can use it with ads for free, which is not always the case for a lot of programs anymore (and no, the ads aren't that space-wasting...)
For Office- try to play a bit with all programs. At the beginning I used to use the Office for Mac suite (it was 2004, hey!
used it until 2006), but mostly the excellent Textedit, the standard editor provided with OS X (it was a lot more barebone than its now). Used to have iWork since it came out, fell in and out of love, going to come back there with '09. I didn't like Bean much (lasted a couple of months), but it was surely better than NeoOffice (too slow) and OpenOffice (I need to write a paper, not to program the thing...).
So test them and use them according to your needs and habits; .doc and .rtf files are both a good choice in that first phase, since it's what runs everywhere. Afterwards, if you choose a not-.doc based application, you can easily convert. Mind that in sharing you don't give the poor Windows user an RFTD (I remember having some from Bean days), because it's a format not supported as a file, it will read as a directory.
Ah, and for any uninstalling need (so that you won't have many orphaned files around, once you've dropped the icon in the trashbin): AppCleaner. Works marvellously. Drag-and-Drop, give the ok, go back to the finder and empty trash
