I found it slow. Also, just remembering this now but I came in to work one morning only to be questioned as to why I was downloading GBs of data while I was out of the office. I guess Dash was refreshing the local copy of all the docs every night. Uninstalled it right away.
Slow? It's insanely fast on my 6 year old desktop and doesn't download "gigs" of docs every night...also, what kind of workplace monitors individuals net usage then gets upset at them for downloading "gigs" when their job is to program.
This was my first time seeing DevDocs, it's awesome! I've used other all in one doc solutions but I always end up going back to google because they slow down once I add all the languages and packages I use.