I've done about a half dozen with hackberry now. I get great reviews on the aesthetics of the wood, very smooth looking stuff, light buttery yellow color. They shoot pretty good and seem to be holding up fairly well.
I like working it green when possible because it responds to the draw knife and spoke shave very well if the cutting edge is razor sharp. They peel easily and leave you with a single growth ring with no effort at all. Just remember to seal the back with a couple coats of polly-you're-insane or something watertight. Then draw it down to rough dimension and stand it in the corner for a few weeks to bring it down to 7-8 % moisture before tillering.
Would I recommend it for someone that is going to build just one bow? No. There are better woods. Would I recommend it to someone that wants to build it because they like building bows? Oh heck yeah!