Migrating from a database we quite like to one we do not provides as much fun as surgery.
After the DBA has promoted the database into QA we find our application is spouting Primary Key violations because the sequence.nextval values are below those used within their respective tables. Identity columns. Yet another reason to prefer SQL Server. There's a clear pattern here.
Sure, there are some advantages but we'd take portability over the possibility of having more than one auto-generated sequence any day.
It's interesting catching the impressions of an Oracle expert going the other way. Oracle to SQL Server: Crossing the Great Divide, Part 2. The comments in Part 1 make for a fun read. Especially those that bemoan the developer tools.