Certification isn't just a "nice to have" - it's a hard requirement for certain partner levels. For example, if you want to attain MS Gold Parter in BI, one of the options states:
Your organization must employ or contract with four unique MCP's who each hold at least one of the following certifications:
- MCITP: Business Intelligence Developer 2008
- MCM: Microsoft SQL Server 2008
Effective May 2012, certification requirements will be:
-Two of the four MCP's must each hold the MCITP: Business Intelligence Developer 2008 certification.
-The other two MCP's must each successfully complete one of the following:
--MCITP: Business Intelligence Developer 2008
--MCM: Microsoft SQL Server 2008
--Exam 70-576: PRO: Designing and Developing Microsoft SharePoint 2010 Applications
See how the MCM certification has been inserted as an option? I would not be surprised if this becomes a hard requirement in a future version of the Gold partner program.
Anyway, having a certification in no way qualifies you for anything but it does have tangible benefits and has value in certain circles. In this context, it's definitely a worthy career goal.