First, without using an nginx + fastcgi/Apache/whatever front-end it's not true that just running W3TC scales your site. I was doing that for my own blog and whenever I hit the top of HackerNews my site would go down anyway because Apache is still a beast and you need the proxy to move bytes.
Second, getting a sensible configuration of W3TC including e.g. memcached instead of the file cache is not trivial.
Third, it's not true that a "commodity VPS" server will match our speed. We found that hard drive speed and processors (e.g. Intel Xeon not AMD crap you get at some hosting providers, Amazon AWS included) together made a 2x difference in page-load speed in our tests of various VPS providers.
Fourth, none of that helps you with security. You still have to be on top of which plugins are secure, which patches are faulty, file permissions. Among the obvious security measures, we also have HARDWARE security devices (e.g. DoS and obvious hacking signatures) in front of our servers -- something you'd have to pay a lot for at MT (if you can do it at all).
Fifth, we have awesome WordPress-specific tech support from true experts, something that I'm sure you'll admit you don't get at MT or VPS providers like Rackspace and Amazon.
However I DO AGREE WITH YOU that anyone who is technical and wants to do the tests and research absolutely can produce a system reasonably close to ours. However wouldn't YOU agree that most WordPress users either aren't that technical or -- like me -- simply don't want to deal with it?
That's where we come in.
What I wanted to highlight wasn't so much the technical underpinnings of the offering and why it's important to engineers and geeks, but rather what impressed me based on my initial reactions.
I haven't had a chance to thoroughly evaluate the service since it's brand new of course, but I plunked down my credit card just like everyone else on the waiting list if you're implying that I have a special relationship with them.
I just appreciate good service, entrepreneurship, and what WP Engine represents.
I don't doubt that they're offering a good service, but you can achieve this on your own with the a cache plugin and a reliable hosting service. In todays modern VPS world, $49 and $99 (WP Engine pricepoints) will get you a pretty beefy VPS.
This post is indeed a bit vague on the details, and does feel like a post piece. A disclaimer should have been at the bottom :P
Also, I am curious to know if they're using mod_php with Apache, or FastCGI. The latter of which is more secure. At that point, however, I wonder why they just wouldn't use Nginx + FastCGI for everything and eliminate Apache altogether.
At the opposite side of the spectrum, it does look like they have a few other nice features like being able to snapshot your site and modify things in a staging area, separate from visitors. They don't go into too much detail regarding their backup system, but anything is better than nothing. Interesting to see a new service like this in the WP arena.
Hopefully WP is rewritten in fully OOP PHP5 so that developers can be happier, with some elite caching at the core. For now, it's totally burned me out.