I'm looking at moving from PHP5 to Ruby, and I've recently had another look at the ruby-lang.org site. There's a section on how Ruby compares to PHP(5).

One of the differences is states is that "there’s no abstract classes or interfaces". I'm no OO guru, but wouldn't that be cause for concern? I've been using frameworks and developing in OO now for about 5 years and while I use abstract classes and interfaces sparringly, I've found them useful - especially when developing a custom Database abstraction layer.

To those of you who have come from another OO language to Ruby, and use Ruby outside of the RoR camp, I ask: do you miss not having abstract classes and interfaces? Is your life now easier without them? What are your thoughts on the matter?