Someone on Linkedin asked this question the other day. Here was my response…
I’ve had my eyes on http://www.squarespace.com/ for some time now. Their UI is interesting, scalable traffic, nice tools…i’ve not yet built an entire site in it however. I have heard good things about them from other people.
WordPress is good depending on what you want to do. If someone needs a website, this is a great place to get them started.
Joomla is powerful but you really need to know what you’re doing…and qualified resources are few and far between. There is nothing intuitive about the Admin. We’ve found it to be very good from and SEO standpoint, with some limitations when you start adding modules like Mosets Tree. Lot’s of people say they “know” Joomla but it’s my experience that most of those people are blowing smoke.
The #1 problem with using a CMS is that your site is going to have that “template” look to it. Customizing templates and themes can be arduous.
If you don’t pay attention to your theme selection, cross platform compatibility issues can bite you. Plus all of those IE6/7/8 and FF2/3 issues you though were a thing of the past may sneak back in…not to mention the strange things that Safari and Chrome can do to some CMS Themes/Templates.
Little things like page flicker, alignments, and finding qualified designers who understand how to integrate their look into your CMS can blow your deadlines and your budget.
If you are going to be competing at a very high level, these limitations can hurt your credibility and your ability to deploy.