In development it takes Jekyll 32 seconds[0] to do a full build and I've done my best to eliminate as many performance killing nested loops as possible. If I use --incremental it takes about 3 seconds, so my normal writing flow is to split my browser and code editor and I see real-time live reloaded feedback in 3 seconds.
It's pretty good, but some changes require a full build and waiting 30 seconds stinks. If I could snap my fingers and have a fully compatible Go solution that built it in 3 seconds all the time I'd switch without thinking.
Gojekyll isn't compatible with a few plugins I use and switching ~700 posts, a bunch of templates and a few custom plugins to Hugo isn't worth it for my use case.
On the other hand I'm locked into Jekyll 3.X because I can't get Jekyll-Assets to work with any other version so at some point I'll switch but I'm not looking forward to porting that many templates and posts. If it comes down to it I'd probably end up writing a custom tool to convert everything especially since I do custom'ish things with front matter like create a table of contents for each post. It'll require a bunch of string parsing.
[0]: This is on a 9 year old quad core i5 3.2ghz workstation with an SSD.
