Actually, I only now had time to spend on this: and ended up testing LZF (http://oldhome.schmorp.de/marc/liblzf.html), ported by H2 team (http://h2database.googlecode.com/svn/trunk/h2/src/main/org/h2/compress/).
Turns out LZF is pretty good at speed, although one has to be careful with choosing good buffer sizes, hash table size, and ideally reuse buffers too if possible. If so, it can be bit faster on decompression, and a lot faster on compression.
Numbers I saw (this is just initial testing) indicated up to twice as fast compression, and maybe 30% faster decompress.
Compression ratio is not as good; whereas gzip would give raties of 81/93/97% (for content size of 2k/20k/200k), LZF would give 66/72/72% (ie. compresses down to 34/28/28% of original). Which is still pretty good of course.
These with JSON data.
LZF is block-based algorithm just like all others, including gzip, and is about as easy to wrap in input/output streams.
I hope to find time to actually wrap existing code into bit better packaging (wrt buffer reuse and other optimizations). If so, it could be a reusable component. That may take some time, but in the meantime, source link above allows others to try out code as well if they want to.