A few little things...

Share certain achievements/levels with your guild...
Link items and achievements into chat...
Add the dates you accomplished your achievements
Be able to sort the guild window by things like acheivement points...
Add date you joined the guild...
Be able to preview gear appearance before you buy it or choose it from a quest reward...
Show side by side gear comparisons...

....little things....but now that the log in fiasco is under control maybe we can start pushing for things like these. :)