The main reason is that "datablock optimizations" are off by default. "datablock optimizations" made compiling especially slow when adding large amounts of data, and then adding a lot of files.
1.1o's datablock optimizer is a lot faster, and strings are optimized in their own block, so the whole thing works faster as well.
I got rid of the nifty animation because I moved to using one deflate() call per file, instead of the blocking system of before (which is more efficient). I suppose I could make it use multiple deflates but without synchronization, in order to put the little animation back, but I think it's OK this way.