Certifications show you can study and take a test
They don't demonstrate that you actually comprehend any thing that was on the test. In the worse case certifications can turn off a lot of hiring managers as they got burned in the dotCom bubble boom with unqualified staff but were "certified", it looks like someone trying to take a short cut to actual knowledge and experience.
I think twice about people with lots of certifications, especially in things they have little or no demonstrable experience in. I had so many real estate agents in the 1990's applying for developer positions with a arms length of certifications and bogus years of experience it was sickening. Lots of my peers experienced the same thing.
Look at it this way
Would you hire a graphic designer with a bunch of Photoshop certifications or one with a portfolio of demonstrable work using Photoshop, given that they claimed the same number of years of experience?
Certifications don't make you more marketable
Better marketing makes you more marketable. You should invest in learning how to sell yourself on what you knows and learn how to demonstrate what you know, don't spend money on taking tests about things you partially know in an attempt to prove something to someone.
Demonstrable knowledge isn't about years of experience, it is about demonstration
Spend some time writing an open source application, no matter how trival, that demonstrates your knowledge, put it on GitHub, put it on FreshMeat.net, put links to those sites on your resume.
Spend time writing about development on a blog, people with experience have personal opinions about what they do. Blog about your open source development and your opinions about .Net and its libraries. Opinions, even ones I don't agree with demonstrate your knowledge about something.
I know this will sound silly, but your job isn't what you do, it is selling yourself. You need to be able communicate that as quickly and clearly as possible. Marketing and Sales is all about communication.
Generalists usually make better management
Later on in your career when you get totally burned out on programming, you will want to be able move on up into management or some position where you lead. Generalists can mentor and manager a broader range of talent.
In golf you need to know how to use every club, only knowing the putter won't get you far on a full size golf course.
Being a .Net guru won't get you a management position, it will get you a glass ceiling of Senior .Net Developer. Being able to demonstrate a broad range of expertise will get you farther toward management than being a .Net guru. And it will open more doors outside the .Net world.
Success != scoring good on tests
Think about it, nobody in the software development field that is a big name got there because of some test they took. They all built something or wrote something that demonstrated that they knew what they were doing.
Years experience != proficiency
I have worked with many developers that claimed 10+ years of experience in Java. 9 out of 10 of them wrote code like it was 10 years ago. They had 10 years of doing the same thing they did the first year. 10 years of 1 year of experience isn't valuable either.
The 1 out of the 9 could easily demonstrate their proficiency either with examples or their opinions about current modern Java. The others were still using
Hashmap in 2009 and didn't even know or care about Generics or the
Collections API, this was a negative demonstration of their experience.
Take it personally
If you want to go and take certifications for yourself, to see what the testing organization thinks is important or valuable then there may be some value to it for you personally. It might show you where the holes in your knowledge of a particular technology is and give some direction of knowing what you don't know you don't know.
As a kudo on your resume, I stand by my assertion that certifications aren't very valuable to third parties.