Using Reflection - balancing the issue with 'loose coupling'

Sahil Malik's post on the performance of Reflection raises some issues. While Reflection can bring in the power of extensibility ('loose coupling via Interfaces') it comes at the cost of performance (as pointed out by Sahil). Justin Gehtland's example of extensibility using Factory methods and XML config files concludes with -  "That means you shouldn't do everything via reflection, but its judicious use for something like loading a dynamically assigned class at runtime (but binding it statically to a known interface) is perfectly reasonable, especially if you are talking about a modern distributed application, where the two more important criteria for boosting performance are limiting round trips on the network and minimizing hits to the database. If you can solve those problems, then maybe you can think about how a little reflection affects performance. I find that extensibility is usually a more important factor for me."