From that previous Microsoft product comparison link....
It looks like the biggest differences are the following:
1. Professional has compiler support for 64 bit platforms, Standard Edition does not.
2. Professional Integrates with SQL Server 2005, Standard Edition does not.
3. Professional allows remote debugging, Standard Edition does not.
4. Professional includes SQL Server 2005 Development Edition tools, Standard Edition does not.
So, if you are doing any kind of development work for 64 bit machines, or database involving SQL Server 2005 then you should probably make sure to get the Professional Edition.