I work part time as a bather for one of the groomers at my work (2 days a week), and we have the same 4hp dryer right now. We had a bigger model before, but this one seems just as powerful, and lighter/easier to set up/put away. Word to the wise- it has a powerful kick when you turn it on, and if not set on the legs correctly, will roll and eventually the switch will break. You can buy replacement parts through catalogs (ryans, etc) or I'm sure somewhere online, most things are pretty easily fixed/replaced. I convinced my boss to buy the wall mount bracket for ours, it holds it secure to the grooming table so we don't have to worry about that any more.
I use it on pretty much any size dog, even on my coworkers' 4# chi. For puppies/nervous dogs/longer, more easily matted hair, you can remove the nozzle and just use the open hose- I've used it like that on <8 week old kittens, so it's pretty versatile. Blows the undercoat out of bigger dogs well- it's definitely a hair tornado with breeds like GSDs, shelties, chows, etc. It starts off cool, but once it's been ran for a bit, it's warm air. To speed drying, we sometimes use it in conjunction with a regular hair dryer until it warms up. Sound is equivalent to that of a vacuum- benefit over a regular hair dryer is that the majority of the sound is the unit, which is several feet from them thanks to the hose.
If I had a coated breed, and didn't have ready access to a force dryer, I'd absolutely buy one- it's the worst day ever as a bather when the dryer breaks, and always on a day when we have a bunch of cat baths or heavy coated dogs :< Hope you like it!