Certifications are one of those things that depend on your situation. There are only three logical reasons as a .NET developer to get certifications. Most of the other reasons usually descend into emotional arguments.
- Microsoft Partners require that they have at least 2 certified professionals (with Microsoft certifications in whatever they specialize) in their staff at anyone time, or they lose their official status.
- You have less than 5 years experience in the specific technology, and want to break into something that you don't have experience in.
- The positions you are applying to require you to have certifications.
I have found that companies stop asking you about certifications after you have 3 or more years experience. Hence the reason why most developer with experience will tell you that certifications are not really necessary.
Now, this being said, I have found that a developer with one of the SQL Server or Windows Server certifications will garner a lot of attention. The main reason I've heard managers talking about this, is that you have a broader knowledge, and become more valuable to the company.
I have both Windows Server and SQL Server administration experience (without certifications) and I've found that I get paid higher than people who only have developer experience.