I have been doing them for about a year or more. When I first started I was pretty regular but I have fallen off a bit. I can confirm that yes they do help in firmness and they also help in your sizew too - that has been my greatest benefit but its primarly strenghtens the PC musucles. This means you can use it to delay climax.
I have other reasons for practicing Male kegels - they are very good for overall meale health down below because they make you concentrate your attention to that area.
I do talk at length about kegels for men at my site. its not a sales site - simply me talking about my personal experiences. There are some affiliate links which you can ignore. I also talk about perly penile papules which I have and they have ruined my personal life - no girlfriend etc. You can read about it at Malekegel.net
Ill hopefully be talking about papules here too assuming there isnt a post here already about it!