I generally don't like photomanips for the same reason that I don't like most muscle growth themed art: a lot of artists don't quite understand that the best kind of photomanips, the most believable sort, are small, subtle twists for more pleasing proportions, and "extreme" level photomanips fall into the "uncanny valley," where something is obviously fake and your mind rebels against the idea.
Also, with the near-universal availability of programs like photoshop, there are a lot more bad photomanipulators than good ones.
With the blog BigDudes, the very best photomanips are the most recent ones where he just tweaks them for masculine dimensions instead of inflating them grotesquely. It's actually possible to see him improve: the first few images are unrecognizable masses of grunting overstuffed bulges, whereas the recent ones are sleek, unbelievably massive and well proportioned. Perhaps I don't "get" photomanips as well as others do, but I like to think for a woman I'm more visual about sexuality and attraction than normal. However, it is true that with any celebrity or photographed figure, the more they're airbrushed the worse things get.
Special emphasis should be paid to some of his more robust muscle posteriors and backs. This blog is definitely one to watch for.