This is supposed to be the next wave of web programming. I was trying to program a blog on PHP and got fed up.
Ruby on Rails isn't saving me development time (mostly because I don't know it well) but it's as simple or complex as you want it to be. I suppose if I ever learn it well it might be the thing to use.
I'd say the lack of diverse documentation is a minus.
As said, learn Ruby first and all the clever things people typically do in it.
Rails is fine, and is far better than PHP in that you've got a decent MVC framework right there and Ruby's API (i.e. no giant namespace of stupid-ass functions). I am primarily a Java programmer, but have picked up and enjoy Lua/Ruby -- functional is a different way of thinking, but it's the languages I use for my personal projects. Ruby feels to me like a mix of Lua and Perl, but even more OOP-ified (good) and with a sizable backing API.
Rails cannot compare to ASP.Net/J2EE in object persistence. ActiveRecord is a bit too hacky for my tastes (for example, it is considered "okay" to use aggregate functions when setting the fields to retrieve when querying). That you can still perform SQL injection using parts of ActiveRecord shows it's just a slightly magical layer over SQL. Nice, but if I'm going to go to the pain in the ass of letting a pseudo-ORM system take over SQL duties that I don't mind, I want it to encapsulate it fully (see: Hibernate/JPA).
Can't seem to beat ASP.Net for RAD web apps... that pile of dorkturds is amazingly useful for getting stuff together and working fast (however, I have many reasons to hate it -- working around its stupid-shit GridView control, its impossible-to-use two-way bindable templates, HTML not being escaped by default in labels...)
blar bl blururrburlubqatb i liek talking aboot teh eterprise xD