I've just done all 4 of the exams for .Net 4.0 MCPD Web Developer. Overall, I quite enjoyed it. I even learned a bit.
Programmer certifications, and particularly the Microsoft ones, get a lot of criticism. In theory they prove someone is proficient in the technology. In practice, by itself a certificate is unreliable.
Microsoft's Partner program insists that companies have staff with certifications. The body shops put their new recruits through a brief course so they can pass and then be sold on. Often, they memorised the questions and answers from internet dumps. It's disappointing to google the exam codes: apart from the Microsoft syllabus, every link is a site selling the answers.
If you're a consultant, or you're going to change jobs, experienced programmers probably have to do the exams too. If you work for a Microsoft Partner you have to do it, and HR departments filter their CVs using it. Really, the best measure of proficiency is years of experience and types of projects. That's real-world practical knowledge. Okay, I would say that, having been doing this for 25 years. But, as the company I work for needs the certificate points, and they're paying, I'm happy to do the exams.
For .net 1 we had to do exams for ASP, windows forms and web services, but most .net programmers then only worked in one or two of those- certainly never windows forms and ASP. I was actually quite impressed by the .Net 2 foundation exam, which covered a lot of basics: collections, threads, tracing, serialization, globalization, encryption. Specific projects may not involve some of it, but a good .net programmer should know almost all of it (even if you have to google the details). Unfortunately they dropped it for .Net 4, going back to technology areas (asp, web services) just like the original .net 1 exams. Now for .net 4 "web" we have asp, wcf and data access (ado/entity framework). Broadly I agree you'd expect all web developers to know those topics, so that's not too bad.
One big problem with certification questions is that they pick on obscure APIs and ASP controls. Now, questions on the validation controls is probably a good basic requirement, but frankly the gridview events are a nightmare anyway, so memorizing them for an exam is painful. The .net 4 asp exam wasn't too bad although there was some API questions that in real life you'd just google. One of the jQuery questions annoyed me too, using an unusual API detail (I think an older syntax) when they could have used a better, clearer replacement.
The older exams had sections devoted to things nobody ever uses. On the asp .net 2 exam it was mobile controls, and web parts (cloned from Sharepoint, and never used outside Sharepoint). Fortunately there seems less of that in the .net 4 exams, although there's still some asp ajax library stuff in there, plus some dynamic data. The big problem was that jQuery and MVC have moved on since the exam was written. All the questions were about MVC 2, not 3. It's not that the questions were obsolete (there was nothing much about webform views to confuse those who use Razor), it's just that the pace of change is making exams less relevant.
The other exams had little used topics too. The WCF exam covered MSMQ, which I've never seen used in real life. The data access exam was more problematic. Basic ADO is useful, but there was still material about little used dataset features like constraints and dataRelations. There was not much on Linq2Sql, perhaps just as well, but most of the exam was Entity Framework. I know EF is used out there, but I've yet to encounter EF and it seems to be in second place to NHibernate at least for ORM data access. So I did learn something for this exam, and yes, I passed the exam as a novice with no real world experience of Entity Framework. On the other hand, as an experienced programmer I'd feel comfortable doing EF (even if I'd rather be doing NHibernate.)
Two of the exams - the WCF and the ASP Pro exam - had "testlets" with a case study and a small number of questions about the scenario. The WCF was over-elaborate, with source listings and xml, but for all that I thought it was a little more realistic and actually quite enjoyable.
To study, I used the Microsoft Training Kit books, MSDN and for the areas I was less familiar with - mostly EF and some aspects of WCF - a little practice. The WCF exam didn't have a book, so I had to use the .net 3.5 one and look up a couple of subjects (routing and discovery). I skimmed the bits I knew well (the asp/ web side generally). Generally I found you needed a bit more knowledge than was in the books, but only a few things were really obscure. Overall, studying for the exam was interesting and useful. Learning about WCF routing and discovery and EF, things I haven't actually used, did bring me more up-to-date with the .net 4 stack.
A pity Microsoft's "congratulations" email contains a link to a blog that closed 2 years ago.