Is there any advantage to using Alien Skin Bokeh tool over simply using a gradient to blend a sharp layer and blurred layer?
Fading between an original image and a blurred image does not look physically correct. You end up with a "glamour shots" hazy effect the in the transition area. Bokeh does the correct physical simulation to make the transition look like what a real lens would create.
Bokeh will also allow you to create the effect you are after without all the manual work. When used in conjunction with a Smart Object, you can go back and easily tweak it until you get the look you are after. This will save much time over having to do everything manually in Photoshop.
Here is an example of what we mean.