To achieve parity with upstream providers, we will need accurate and up-to date information on their platforms. Users will also be able to define and build custom platforms.

There is a great quora thread for discovering specs of different platform. This levelten post also gets into the weeds with versions.

(Not sure if we care about the specifics yet, but they're provided nonetheless.) (source)

• Ubuntu Lucid (though also testing CentOS) (JM: I suggest 12.04.2 LTS Precise Pangolin rather than 10.04.4 LTS Lucid Lynx)
• Memcached 1.4.5
• Apache2 (mod_fcgid) 2.2.14
• Percona 5.5
• Drush 4.6 (drush 5.8 aliased to drush5)
• PHP-CGI 5.3.2
• Apache Solr 3.5

Versions documented on Acquia Docs. (Acquia accounts required, unfortunately.)

• PHP-FPM 5.3
• nginx
• MySQL
• Redis
• Apache Solr
• Drush 5.1
• Varnish