It does emit the Computed attribute when the field is indeed a computed column, as determined by the driver. I see it is limiting to do it like this and based on type it's limiting too, simply because it can be 'timestamp' is not a type which data is generated on the server.
We can easily add a setting in the frameworksettings file so it ends up in the list of settings to set for a field. The drawback of this is that it's a little cumbersome to set that setting for all timestamp fields. Some add these kind of fields to every table. So for now we'll add it automatically for timestamp on sqlserver to the templates, and we'll add the setting to the frameworksettings file for the fields. You can use the setting for fields like CreatedDate, and leave timestamp fields to the template.
(edit) It's a bit difficult to add the setting, or better: to use it in practice in the edmx template. The problem is mainly that the settings are defined on the entity field type and have effect on the target field. But there can be multiple entityfields mapped onto the same target field (e.g. you have 2 entities mapped onto the same table). This gives a problem as you perhaps enabled the setting on field F1 in E1, but not on F2 in E2, both F1 and F2 are mapped onto tablefield TF1.
So we'll go for timestamp + sqlserver for now. In the next v3.x version we're adding conventions and allow more changes to db table fields, e.g. allow you to edit the IsComputed flag on the table field, something which isn't possible now in the UI.
