They didn't just design a "frame" for the site, they designed the content as well. This is what I believe truly separates the "ok" designs from the great ones.
Some examples of how they have designed the details:
- the headings of their tables (data grids) have a subtle, attractive gradient background and a subtle banded scheme with a nice hover/highlight effect
- every screen shot (features, resources pages) is attractive and neatly cropped
- the "price tag" on their pricing page is impossible to miss, yet matches the site perfectly
- the icons are used consistently throughout the site
The method I use to inject quality design at every level of a site, is to design (with whatever tool you prefer) several pages in addition to the home page and sub page. This requires a great deal of preparation. You have to know what content you are going to have, and where it will go. You have to think the content over thoroughly during the design phase. Often it's hard to visualize content without actually having a site design, so I find it's something of a back-and-forth process. Work on the main site design, develop a look; then go design the content pages, go back and adjust your layout...
Design is a living process, it can never all be done "up front", and there is no such thing as taking a template and running with it forever and ever. I'm not trying to create job security for myself, but I do know that well designed sites like CampaignMonitor don't happen by accident.