I find tooltips can be very useful and I don't find them intrusive at all if they are done well. On the other hand I have a drawing app that shows co-ordinates as a tooltip as soon as I move anything and it often gets in the way.
It's really down to the delay before they show.Having data in a status bar may be less useful as you'll need to move you eye to see it, if you're trying to select the right icon from a group that could be really annoying. It'll also always be displaying things so will be constantly competing for your attention, anyone who's read a web page with flash ads will know all about that...
IMHO BTW on the annoying flash ad front...There was a once a "feature" in the Safari browser that caused the page to completely freeze when you scrolled the page, it was a very good way of stopping annoying ads but alas they removed it :-(
-- Nicholas Blachford www.blachford.info "You made your point, you will be deleted."