I was going to shoot a video, or write up a article on Flash photography today, but never got around to it. So I'll try to sum it up here...
Flash photography is brilliant. Well, it CAN be brilliant. Today, flash photography is not as tedious as it was when manual flashes were being used. Until I decide to change systems, I'm using an older model Vivitar Manual flash mounted on my hot shoe adapter. Do I like using it? Yes. Is it difficult to control? Yes. Do I wish it was digital? Absolutely yes.
These days with the new flashes, (i.e. SB-400 - SB-800/900 or Canon series) flash photography offers much easier to use systems, and can really deliver great results.
Photography is all about lighting. That's really what separates a Photographer from money-spenders and amateurs. Now please don't get me wrong on this, but it's kinda true to an extent.
I think there are many advantages and benefits from flash photography. When mixing flash in with natural light, you can get brilliant outcomes. You just need to learn how to control the light. You don't want to take away from the natural light, or take over the natural light. You just want to add some flash to give a boost. And it looks great.
For studio settings too, using the flash is great. Almost anywhere you are, you can use a flash and have the advantage of a 'fast' enough shutter, while having natural and nice images.
I'm saying this from experience. Firing the flash will give great sharpness to the image.
Also, you can use the flash as a "mini" substitute for a strobe light. So you can use it to lighten up backgrounds, give background color, give subject color, pretty much anything you want as far as lighting is concerned.
I highly recommend external flashes. Do I think they are a good full substitute for studio monolights? No.
But for many many many shots, flashes can give great detail and benefits.