Read this before you swap...

That's exactly what happened to the engine I bought before I got it. They thought that a ring land chipped, but after looking it over closer when I bought it I noticed half of the valve seat was missing. The main issue is just that they are aluminum heads with hardened steel (or whatever material) seats, so thermal expansion can be a issue. Like was mentioned earlier, I think it only really tends to happen when they get too hot. My engine was supposedly out of a police car, so I can buy that. I'll see if I have a decent picture. I know I have one of the beat up head, but not specifically of the valve seat.

And even though the issue may be all over the net, it's probably more than likely because it's on the only issues these engine tend to have. However, there are over a million Hemis already on the road, so what percentage does it really affect is the question. Hardly anyone ever gets online to praise stuff, they only post when things go bad, so if you look up issues for any particular car/engine you'll really only ever see the worst things people have to say. They also say Hemis like to spit rods out the block, but if you look that up almost every instance involves sucking in water (rainy day, big puddle, etc.).