Well - i use formats as well as any other templating system. Everything depends on what i'm actually trying to do - if it's a some documment (file) with some information prepared dynamically i use the templating modules. If it's a simple task i use formats.
Simplicity - that's all. Formats are really great when you have to prepare some reports or something like this - when the documment consists of many *almost identical* lines, and that's what i use formats for ;-)

Greetz, Tom.