Since Class::XSAccessor now supports constructors (see previous journal entry), there's everything in place to implement Object::Tiny in XS. Hence you can find Object::Tiny::XS 1.01 on CPAN very soon. It's been uploaded to PAUSE.
The following benchmarks can be found in the distribution. They're comparing O::Tiny::XS to O::Tiny and Class::Accessor::Fast.
Benchmarking constructor plus accessors...
Rate accessor tiny tiny_xs
accessor 107325/s -- -40% -57%
tiny 177837/s 66% -- -29%
tiny_xs 248931/s 132% 40% --
Benchmarking constructor alone...
Rate accessor tiny tiny_xs
accessor 168659/s -- -49% -57%
tiny 330831/s 96% -- -17%
tiny_xs 396844/s 135% 20% --
Benchmarking accessors alone...
Rate accessor tiny tiny_xs
accessor 331/s -- -16% -54%
tiny 395/s 19% -- -45%
tiny_xs 715/s 116% 81% --