How to choose between ORMs?

[Alec Taylor]

SQLalchemy and Storm are a few of the popular ORMs out there.

Personally I have been using web2py's DAL.

Other than form generator availability, 'print as raw SQL', multiple
primary keys, widgets*, `check` conditions and compatibility with
OracleDB, Postgres, SQLite and some of the NoSQL systems; what else
should I be looking for?

Thanks for all suggestions,

Alec Taylor

*not sure if widgets should be a requirement; by widgets I mean
annotation of db schema to specify which widget to use with the form
generator

PS: Will likely use this ORM with: Flask, Bottle or Twisted Matrix