I ran the first benchmark linked in the readme on my mobile phone (2013 Moto G, i.e. old mid-end phone) and on my laptop (Thinkpad X230 i5-3320M), both on Firefox:

    Sprint (phone):    33.1 kops
    jquery (phone):     8.8 kops
    zepto  (phone):    10.1 kops

    Sprint (laptop): 1435.2 kops
    jquery (laptop):   49.2 kops
    zepto  (laptop):   65.9 kops

Not bad, if that translates to real world performance.