Ajax is an important development for Web applications, and its importance is only going to grow.

Building technical systems involves a lot of hard work and specialized knowledge: languages and protocols, coding and debugging, testing and refactoring.

I'm not sure that you can say definitively that some roles are better filled by consultants, but I would say that some projects are better handled by consultants.

If you need to take a step back from day-to-day operations and plot out the long-term direction of your user experience strategy, consultants can give you a perspective you can't get on your own.

At Adaptive Path, we've been doing our own work with Ajax over the last several months, and we're realizing we've only scratched the surface of the rich interaction and responsiveness that Ajax applications can provide.

Problems with visual design can turn users off so quickly that they never discover all the smart choices you made with navigation or interaction design.

Also, if nothing else, writing this book has really changed the way I experience bookstores. I have a whole different appreciation for the amount of work packed into even the slimmest volume on the shelves.