Environment:Debian 5.0, PHP 5.3.3, MySQL 5.1.50, Doctrine 2.0.0BETA4, Annotations
Create a new entity with a column type decimal @Column(type="decimal")
Run the CLI tool "migrations:diff"
Run the CLI tool "migrations:migrate"
If you run "migrations:diff" again a new migration will be created with an ALTER TABLE that only affects the columns of type Decimal. You can apply these new migrations and generate more using Diff ad nauseum.
My assumption is there is a mismatch between the Migrations Diff and annotation's defaults, causing it to continually identify decimal columns as requiring a migration.
To avoid this issue manually set a precision and scale, everything will then work as expected.