I liked Concrete5 when I was playing around with it. I was very excited by its potential; especially looking at projects where maybe WP was overkill.
Where the bottom fell out was in two areas:
1. Paid plugins
I cannot rationally tell my clients 'this software might have a few cases where it is easier than WP to use and manage; but you'll be spending several hundred dollars replicating free functionality available on WP'.
Its a non-starter.
2. The software still looks kind of 'hokey' compared to WordPress
WordPress has lots of issues and there are a ton of other great alternatives. But, its like Facebook vs. all other social networks -- you go where the people are because it makes everything better.
1. Yes, there is a lot more of everything available for wordpress (free and paid plugins/themes). I think this is what a lot of the comments here are saying about why Wordpress is so prevalent... not because it's good necessarily, but because it just has so much stuff available for it.
FWIW, I build custom-designed sites for my clients, and I deliver complete sites that don't require any additional functionality. I don't even bother telling clients how to install new plugins, so for my situation this is a moot point.
When I do pay for plugins, it's because the functionality it provides would take me much more time to build myself (so if my rate is $100-150/hr., paying $30 or $50 or even $200 for something that would take me 4-8 hours of work is a complete no-brainer).
2. Not sure what you mean by "hokey"... the front-end is entirely designed by the person building the site, and the back-end uses Twitter Bootstrap (as of version 5.5 which was released last year). But to each their own :)
Where the bottom fell out was in two areas:
1. Paid plugins
I cannot rationally tell my clients 'this software might have a few cases where it is easier than WP to use and manage; but you'll be spending several hundred dollars replicating free functionality available on WP'.
Its a non-starter.
2. The software still looks kind of 'hokey' compared to WordPress
WordPress has lots of issues and there are a ton of other great alternatives. But, its like Facebook vs. all other social networks -- you go where the people are because it makes everything better.