Yes, this may have been true 10 years ago when installing everything meant getting the source , setting compile flags for everything to work together and updates were applied manually.
These days I can have Ubuntu , Apache , PHP5 , Mysql and Wordpress all working happily on a VPS in under an hour.
On the other hand there are other considerations like maintenance , security and scaling that it might be nice not to have to worry about.
Well, sure, LAMP is easy to set up if you're working in PHP; that's one of the huge advantages PHP has over most other options. You want to set up and deploy to a Rails server, though, that's going to be a bit more effort.
I've actually had an easier time setting up Phusion Passenger with Apache than I've had setting up PHP. Ease of deployment isn't necessarily a major advantage in PHP's corner anymore.
Like Phil said, it doesn't take more than an hour if you're feeling lazy about it. I've automated it with Chef, but I haven't timed it or anything. Less than 10 minutes for sure.
Rails is not the difficult after you have done it a few times, just line up your console commands and get to work most of the time is waiting for stuff to download/compile.
These days I can have Ubuntu , Apache , PHP5 , Mysql and Wordpress all working happily on a VPS in under an hour.
On the other hand there are other considerations like maintenance , security and scaling that it might be nice not to have to worry about.