On your main question:
I'd like to know your opinion on
whether or not certifications of your
employees have any way of influencing
whether your company gets a contract
or not.
In short they could do, but only under a specific set of circumstances. For example if you developed SharePoint solutions and wanted to get a contract to deliver a project for Microsoft, or on behalf of Microsoft (for one of their customers). Do you expect Microsoft to offer this work to anyone other than an organization with certified staff, or a certain level of partnership certification? Perhaps the more important thing here is that the organization is a Microsoft certified partner. However to achieve this you no doubt need to have Microsoft certified staff.
On your follow-up questions:
Do prospective client look at
certificates at all? Or is the amount
of experience/projects completed the
only thing we need to worry about?
They may look at whether the company is a Microsoft certified partner with a specialization in the matter that they are dealing with. If they are looking for expertise they may start by searching the Partner directory that Microsoft offers. Any sensible company will look at your experience but psychologically a certified partner feels safer to someone working in a procurement department.
This will not make or break you if you are remarkable at what you do. If you are average then additional things like Microsoft certification at the partner level can help.
Are there any 'premier' developer
certifications that do matter? For
example, is it reasonable to ask to be
paid more for a developer who is a
Microsoft Certified Architect (we have
only 3 in the country, BTW).
Why not but the people who have these certifications are remarkable in other ways, and deserve to be highly paid. You won't get a shot at these certifications if you don't have a lot of other attributes. This also means there are lots of better things to be doing before you get to the point of attempting these.
Are managerial certifications worth
investing into? I know that MBA is
undoubtedly very powerful, but I'm
talking about things like Certified
Scrum Master, PMBOK, PMP and the like.
An MBA is not an industry certification. Most HR people tend to treat education and certifications as separate but related things. Industry certifications are often worth having for the day that you deal with someone who isn't able to understand the depth of what you do on a daily basis (eg. anyone not working in an IT or technical capacity).
Does MVP status matter?
Perhaps. It can be used to market your company.