Since Eclipse Ganymede realease (3.4) the PDE Add Dependency Plugin Feature behavior changed a little.
As you can see on the following screenshot taken just after the addition of a dependency on Draw2D plugin , the PDE now automatically fills the Minimum version attribute with the current version of the plugin we depend on.
This is a good thing to enforce developers to explicitly add the required version of plugins that we depend on. Nethertheless it can be sometimes anoying.
One of my plugin needs to still works on Eclipse 3.3. To ensure this compatibility I have to manualy remove the minimum version because my clients Eclipse installation certainly get Draw2d 3.3 and not 3.4.
Just take care of that and enjoy PDE ;o)