Nope; there are quite a lot of "uncool" things that can be done using AJAX methods.
here's one for example,
Send Email When An Hyperlink Is Clicked - High Rankings Search Engine Optimization Forum that I put together.
Another functional use is the "Fast Reply" text boxes on many forums. Urchin (Google Analytics) is another example.
AJAX methods got something of a revival when Gmail appeared on the scene, from then on it became trendy to use it for just about everything.
Just don't use it for including any content that you want the Search Engines to see.