I started minoxidil in June of 2002 and switched to the foam in 2006 with improved results over the liquid. (lots of thickening, moderate regrowth, and a ton of vellus to terminal hairs on hairline) It works better for me. I can't speak for anyone else, but I'm sure you'll find someone who tells you the foam is completely ineffective and those that will confirm how great it is.
Like any minoxidil product, be it liquid or foam, not everyone will respond the same. Just take a peak around the success stories forum and you'll find quite a few guys that have had regrowth with the foam---pics included.