Underneath the good looks, OC client websites come with valid code. Here's a before and after for the recently launched Adec Group site.
We put in extra hours at OC in order to follow web standards and best practices. You'd think something called "best practices" would be par for the course, but it's surprising how many sites seem to completely ignore XHTML validation. I think the biggest reason for invalid code is that you can really snarf up a site's XHTML and modern web browsers are so forgiving the site still looks normal, so nobody bothers to fix it.
Properly validating a site against the W3C Validator gives a lot of advantages.
We realize you don't always have complete control of a site's XHTML. Sometimes you have to embed inflexible, invalid code to mash-up content or apps like Google Maps, YouTube, Facebook, ShareThis, etc. Other times the site's users may type in invalid or duplicate tags and break validation. At the very least it's worth starting out valid.
Meta keywords are very rarely valuable, so we don't use them. Rather, we recommend sprinkling keywords into the pages you are writing. Also, the lack of words on the homepage was a design decision, which while not optimal, also shouldn't be a detriment if the page has a meta description, page title, and well formed menu.
I'll point out that this site is hosted on a client provided shared host. We couldn't do the full tune-up on some things due to lack of control to recompile Apache. Had we been given control to enable gzip or deflate the site would likely score in the 92 range (due to lack of CDN usage).