Is there any evidence "Masai Barefootin'" is any better than any well
constructed shoe.

The articles that I could find where quite limited but this is what i found.

1) Changes in gait and EMG when walking with the Masai Barefoot
Technique. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16169641&dopt=Citation

According to a journal article comparing Masai Barefoot technology to
regular shoes shows that the persons GAIT (walking pattern) slows down
and also increases the use of muscles that work on the ankles with
specific observed increases reported in the Tibialis Anterior
( http://www.exrx.net/Muscles/TibialisAnterior.html ) and also in the
gastrocnemius (http://www.exrx.net/Muscles/Gastrocnemius.html). They
concluded that it is a useful tool for training lower leg muscles when
compared to regular shoes. However they also mentioned that those with
knee conditions should be cautious about wearing Masai Barefoot
technology shoes.

2) Effect of an unstable shoe construction on lower extremity(legs)
gait characteristics.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16209901&dopt=Citation

Another Journal article that I found compared the Masai Barefoot
Technology shoes with a stable control shoe. They found that the
"unstable" Masai Barefoot shoes had a positive effect on movement.

3) Changes in gait characteristics of a normal, healthy population due
to unstable shoe construction.
http://backtowork.co.uk/mbt/Hallam1.pdf
These researchers find that Masai Barefooting technology promotes less
forward lean during walking and suggest that a more upright posture is
acquired when compared to .The findings also find that there may be
reduced weight and strain put onto the lower back. There overall
finding is that the unstable Masai Barefoot technology may reduce the
incidence of musculoskeletal problems.

Overall the research on this subject is rather limited and has with
very small test sizes which means that the evidence is not considered
high quality statistically.