It is worth it from a design standpoint, and in my experience the only Mac I've owned previously is my iBook G4, and 80% of all Macs I use or have used are PPC. I know the speeds and things they're capable of and frankly don't need the Intel machines that I would pay 3 - 4 times more for if gotten new.
I just got my iMac G4 off eBay for $298 at a Buy It Now price and it looks brand new and functions as such. It has Leopard and let me tell you it's faster than my Tiger iBook at 1.33ghz with it's smaller 1.25ghz and same 512mb Ram. I surf the web and do school work and like music, and it will be the home of my iPhone after I get an Airport card for it.
I personally would never bid over $350 for one of these machines until someone works out that Mini idea. It is though a technical impossibility thus far, as the screen will NOT connect with any parts found in the iMac or Mini. If you're really big into circuitry you may find some workaround, but not one person has yet. In the end, if you do get a Mini in the base, and the screen doesn't work, you'd need an external monitor. In the end, you just sacrificed time money and effort doing something ergonomically awkward.
The new or used Intel Mini is now sitting inside a dome shaped base (with or without a useless LCD), and the external and all the components are hooked up to an iDome. It would be better to leave the Mini be and not waste all that.
To answer your question about is it worth it - just a few things for you to think about. Apple is going to drop PPC support someday supposedly soon - a year or 2 down the road. So even basic updates may stop coming your way. The machine isn't deadly slow, but it isn't screaming fast - I'm just saying I wouldn't recommend that those with blood pressure issues try to use iMovie or iDVD on a daily basis. I have iBook and a souped up HP tower with Vista and XP on 2 hard drives, and all my media is on there, and I use that for heavy lifting. So owning the iMac is basically my luxury lust machine. It is my favorite computer of all time, especially from a design standpoint, and I'm very glad I can now call myself an owner of one.
Bottom line - keep it cheap. Don't pay more than $400 overall for one of these computers. Don't expect the latest and greatest in software to come easily if at all, and remember that it's a 1.25ghz PPC, so don't rely on it for graphics. For basic daily use it is an ideal machine, combining practicality and ease-of-use in 1 little space saving design, as the arm allows the screen to go farther than any screen has gone before. For the price, I would say it is well worth the money. Maybe upgrade the Ram and use an external to back up things or store what you don't need every day. Other than that, it's a great computer.
Sorry that was so long - I'm passionate about this machine.
