I know this is off-topic, but I hear only two (and a half) bells: M$ entourage vs. Mail (or Gyazmail). I'm a very happy, very satisfied Eudora user since years. The lite version is free, but you get to see ads. I have absolutely no problem with that. Everything works fine. The only reason I'd switch to Mail would be the integration with addressbook etc. I've given a look to entourage on a PC and personally I would have no use for most of it's features, it's too big, too heavy. I like eudora because even on my clamshel iBook running Jaguar it launches almost instantly, it is light, fast and straightforward.
Most of these observations apply to the Office suite too: too big, too heavy, too many (useless) features. Of course this depends entirely on the type of work you're doing: this is just my personal experience. If and when Apple is going to make an iOffice, I'd like it to be light and straightforward. No bloatware please!