Your blog post suggests using MsgPack as a drop in replacement for JSON for client-server communications. In that context every encode/decode operation on the server would be matched by one in the client browser. The <5% gain in performance on the server (and I think that is generous) cannot possibly make up for the performance hit of a javascript implementation of MsgPack.
When MsgPack was written a lot of JSON in the browser was still not native so an argument could be made if you desperately needed that bandwidth and it worked better than average for your specific workload. That is simply not true anymore.
Comments
Your blog post suggests using MsgPack as a drop in replacement for JSON for client-server communications. In that context every encode/decode operation on the server would be matched by one in the client browser. The <5% gain in performance on the server (and I think that is generous) cannot possibly make up for the performance hit of a javascript implementation of MsgPack.
When MsgPack was written a lot of JSON in the browser was still not native so an argument could be made if you desperately needed that bandwidth and it worked better than average for your specific workload. That is simply not true anymore.
i'm using it in Flash, so there is absolutely no JavaScript involved in my case...