Squarespace may be one of New York’s better-kept secrets. The company operated largely under the radar since its founding in 2003, until Accel and Index Ventures invested $38.5 million in 2010. That was a valuation of more than $100 million. The company is up to 80 employees. Oh, and it’s been profitable pretty much from the start, with users and revenues doubling each year.

Squarespace garnered palpable excitement from a crowd of 750 at last month’s NY Tech Meetup, when founder Anthony Casalena demoed the much-anticipated sixth version of the service. They have a right to be excited — anyone following the company has been waiting for Squarespace 6 to launch for almost a year.

Casalena, who admits he’s “bad at PR,” is in no hurry to rush out his product’s massive upgrade. It’s been in private beta since October. (Sign up for that here; the company pushes invites often). Squarespace itself is running on sixth version, and some users have complained about the long wait. “A lot of people look at it and say, ‘Why isn’t this out?'” he said. “But it has to be the platform that gets us through the next half a decade.”

When it’s officially unveiled, Casalena wants this version to be so perfect and untouchable that even the undisputed CMS leader, WordPress, will be threatened.

It is a very, very lofty goal. Recent data shows WordPress is used by almost half of the top 100 blogs in the world, an increase of 32% over last year. The next closest competitor is homebaked CMS systems (yuck), followed by Movable Type. Squarespace powers zero of the world’s top 100 blogs.

In fact, the company mostly serves smaller blogs and businesses. It has tens of thousands of users, Casalena said, compared with WordPress’s 73 million and Tumblr’s 51 million. The key is Squarespace’s users are all paying a monthly fee. Squarespace is positioned as an alternative to paying some developer $5000 to make a site.

But, especially with Squarespace 6, Casalena said the platform is ready for adoption from publishers of any size. Version five, while excellent, “wasn’t a developer’s dream come true because they couldn’t get into all the code,” he said. The new version is more open for developers. The company is completely capable of hosting high volume sites and is building out programs comparable to WordPress’s support staff.

Still, he isn’t going to fight for the business of the world’s top blogs. “Are we going to get News Corp. onto Squarespace? No,” he said. “But we could take the smaller sites or sub-sites and get them up and running really quickly.” Old properties have too many legacy problems; for new properties, Squarespace is a natural fit, he said.

Aside from the open code, Squarespace 6 boasts flexibility that allows each page to adjust perfectly to the browser or device it’s loaded on. The back end offers a clean and pleasant experience with social configurations, drag and drop galleries, and full analytics. And, as with version five, it’s easy enough for a non-developer like myself to get up and running.

CMS woes (a topic I dedicated 2000 words to in Adweek last year) remain an unsolved problem on the Web. The industry looks the way search engines looked before Google, Casalena said. “It remains a problem, and it’s what keeps us going at it.”