Here is a closeup of my triple:
All three rings are Shimano Ultegra and have never been changed. They probably have at least 12000+ km on them. I've been pretty good about changing the chain regularly although at this point I'm pretty sure that the rear cassette is in need of changing.
If you compare the middle ring with the two outer ones, it looks fairly worn (shark fin pattern). Is it bad enough to need replacing? If I just change the chain and rear cassette will I be entering a world of pain?
UPDATE: Thanks for the advice so far. I have a new cassette and chain standing by but would need to order a new middle ring since it's a bit exotic (one LBS didn't know Shimano still made Ultegra triples). I know that there's a lot of km's on these rings (mostly on the middle one) and I'm also familiar with the "if it still skips, try changing it" philosophy, but I was hoping for a more objective answer. Something about the wear pattern or what to look for if I put a new chain on?