I found the 9 points AF, ISO 3200, raw 5fps with 11 buffer, color setting, view finder, metering, body build and feel way better than XT... Also the custom function 16 "Safely shift in AV or TV" is incredibly useful while shooting indoor stage performance involve motions because lights are constantly changing in some situations.
In fact I used to own XT and 20D too.
However, I just changed to 30D recently because I needed the larger buffer size but not too much $ for a higher upgrade, I tried to believe 20D have no difference than 30D but it does after I used it for a month with 4k shots... worth the extra $100 to upgrade for extra few frames buffer, different color setting and a larger LCD.
It really depends on what you use ur camera for; speed vs different view range with glass
Rumor says 40D might come out in Sept, so 30D price might drop...