The IDE locks up so bad that I can't upload other sketches - I had to move to a mac (with 0021) to comment out the Serial.print(); in the offending code.
In my experience the IDE didn't lock up for longer than 6 seconds -- go slow and be patient (and don't click the Tools menu). I was able to reprogram it from linux by repeatedly clicking the "Upload" button a few times (waiting between clicks), ignoring the error about /dev/ttyACM0 -- it got through eventually.
As I mentioned before, I suspect that the code running on the new Atmega8u2 chip on the Arduino Uno boards is to blame, simply because there are problems accessing the port outside of the Arduino IDE entirely (verified with minicom). Perhaps it's only using half-duplex serial, so while it's busy sending it can't do anything else -- that's just a guess though. I suppose the bootloader (optiboot) might be involved too, but now I'm really taking shots in the dark.