Alright, I ran a few benchmarks myself.  In rigorous mode regex_v8 has the same performance on my 2013 Macbook Pro and an 8-years old i7 CPU (Linux).

Here're results of "perf.py -b raytrace,spectral_norm,meteor_contest,nbody ../cpython/python.exe ../cpython-git/python.exe -r"


fastint5:

### nbody ###
Min: 0.227683 -> 0.197046: 1.16x faster
Avg: 0.229366 -> 0.198889: 1.15x faster
Significant (t=137.31)
Stddev: 0.00170 -> 0.00142: 1.1977x smaller

### spectral_norm ###
Min: 0.296840 -> 0.262279: 1.13x faster
Avg: 0.299616 -> 0.265387: 1.13x faster
Significant (t=74.52)
Stddev: 0.00331 -> 0.00319: 1.0382x smaller

The following not significant results are hidden, use -v to show them:
meteor_contest, raytrace.


======


inline-2:


### raytrace ###
Min: 1.188825 -> 1.213788: 1.02x slower
Avg: 1.199827 -> 1.227276: 1.02x slower
Significant (t=-18.12)
Stddev: 0.00559 -> 0.01408: 2.5184x larger

### spectral_norm ###
Min: 0.296535 -> 0.277025: 1.07x faster
Avg: 0.299044 -> 0.278071: 1.08x faster
Significant (t=87.40)
Stddev: 0.00220 -> 0.00097: 2.2684x smaller

The following not significant results are hidden, use -v to show them:
meteor_contest, nbody.