Hmm, what's that old saying about a free lunch :-?
Decompression speed is a problem. In due course, a version with
approximately 40% faster decompression will be available. I have
done significant work on it since bzip2 was released. Compression
speed improvements are harder to obtain.
For many people, including me, the performance loss is an acceptable
price to pay for shorter download times, etc.
J