Pros/Cons of PSD mockups vs. HTML mockups

I've read some articles (this one and this one) recently that are opening my eyes to HTML mockups as opposed to the usual PSD mockups.

In the article they cite certain pros:

• Changes are a lot faster (including changes to colors, and to some extent to fonts).
• When you're laying the page out as HTML, you're showing the client something a lot closer to what the final product will look like.
• They can see the effects of a liquid layout by changing the size of the window.

Cons:

• Not all visual designers can create a mockup in HTML. It will have to be a two person task. An HTML person and a Photoshop person.

What do you guys see as pros/cons to either approach?