City Desk (as I've said elsewhere) is very powerful in its own right, but the telepark templates add that little bit extra to make implementation a lot easier and the end result much more polished.
Using professional templates has helped me on three counts: Firstly, it got me up and running quickly - although I was on my second iteration of this site before I discovered telepark; secondly, it acted as a learning platform by providing professional code to examine and to play with and thirdly, it provided a basis for the current much adapted version, which does more or less exactly what I want it to do.
The flexibility provided by a customisable template allows for rapid development of web sites to match customer requirements. Using my original agency licence (no longer available, I think), I've used vantaa for a previous version of this site, this current version, but also for the PaceMetrics and Dealing Systems sites. As you can see, each of them has it's own unique look-and-feel, which was implemented literally by changing a few parameters within the template.
If you want to get up to speed quickly with a content management system and still achieve very professional results, then check out the telepark site.