Don't buy the Eris. It was a great little phone when it was released, but even then, it was already considered to have outdated hardware. Wait for the Incredible to come back in stock if you insist on going with HTC.
Are you like 12 or something? Anyone who would pick an Eris over the Droid x must not be thinking straight. And I can assure you that any piece of hardware from Motorola is a lot nicer and better made then anything HTC could make
As a corporate sales rep, I'd say don't settle for the Eris...you'd pretty much be shooting yourself in the foot. As for as Motorola goes, they DID fall off for a few years but, they have totally and completely redeemed themselves with the release of the Droid..and it's only going to get better! If you've made your mind up to leave the Droid on the shelf, I'd personally wait for the Incredible.
P.S. - The Eris is ALREADY discontinued, and I'm glad! Haha!