It has become rather popular since simple methods of installing them side-by-side have been publicly described... it's moved from being an interesting feature really to something that's just trivial to implement.
Good for the consumer, bad for the hosts who used it for a niche.
Jacob - WebOnce Technologies - 30 Day 100% Satisfaction Guarantee - Over 5 Years Going Strong! Website Hosting, PHP4&5, RoR, MySQL 5.0, Reseller Hosting, Development, and Designs
PS. Why am I laughing? Good times should last forever!
The good tomes roll on, for sure, they're just never as grand as they were when things were just rolling out. We've supported PHP5 since the second release candidate for 5.0, but at that time there simply was almost no market for it, so we chose to release the script we use to do the intiial compile and upgrades, to help build the availability and market for PHP5 hosting.
I really don't regret that at all, since it gives the clients more choice of where to go. Competition is good for everyone, and we still have some other things to keep our edge, and are always looking at more tools to continue it.
Mostly PHP5 still belongs to the developer market. Developers love a lot of the features that PHP5 give them, while the general market doesn't really care as most things still work in PHP4 as well... but speaking from experience, the developer market isn't a bad market to target really.