IDE 1.0RC1: is its Optiboot the "old" one?

westfw: Then the Arduino team looks at my code and does more extensive testing than I'm able to do, and decides (hopefully) "yes, this is good and it should go into the official distribution." Then it shows up in the official arduino source base as well. (I believe that this has JUST happened for optiboot 4.4 and the 1.0 source base.)

Out of pure curiosity, do you know why the lock-bits in the official distribution are different? Is it just to minimise the user-visible differences between older and newer Unos? I suppose it's possible a program might try to read from the bootloader flash section, and throw a wobbly if it actually succeeds...

do you know why the lock-bits in the official distribution are different?

Yes. This is http://code.google.com/p/arduino/issues/detail?id=554&q=optiboot One of the sketches I wrote before working on optiboot (fusebytes.pde: https://github.com/WestfW/fusebytes ) was designed to answer the FAQ "what kind of Arduino do you have and which versions of "stuff" does it have." At about the same time, there were a series of bootloader bugs discovered (30k limitation, uno SMD problems, etc), and it was pretty difficult to find out "which version of the bootloader is in your chip." So I thought it would be a good idea if optiboot included a version number, and if that were readable by sketches. (It's that last part that required changing the fuses.) (I couldn't think of any downside to having the bootloader section readable by sketches; it's not like it contains proprietary algorithms that decrypt uploads...) (It was AFTER this was done that it was pointed out that the STK500 protocol also includes a command for reporting the firmware version of the bootload, and now optiboot supports that as well. Sort of.)