eWeek has a review of the HTC Droid Eris, here are some highlights:
The other high-profile Google Android phone, the HTC Droid Eris, takes a different approach. Unlike the Motorola Droid, which slides apart to reveal a physical QWERTY keyboard, the Droid Eris is a single-piece touch-screen device reminiscent of the iPhone. At 4.23 ounces (and no physical keyboard), it is substantially lighter and sleeker than the Motorola Droid, which feels like a miniature brick in your pocket.
However, the HTC Droid Eris comes with a trackball for navigation, which I feel was a substantial mistake; Research In Motion has been eliminating trackballs in favor of trackpads for a reason. Besides clogging with grime after weeks or months of use, the trackball made certain functions of the HTC Droid Eris—such as snapping photos—into mildly annoying chores.

Verdict
At the risk of instigating a flame-war, I feel that the Verizon Droid is the closest that an Apple rival has come to creating a true iPhone killer. Subsequent versions of Google Android will iron out the few kinks, and the Android Marketplace will expand its apps offerings—maybe not enough to challenge Apple’s App Store, but certainly enough to make it a more robust challenger.
The one drawback to the Verizon Droid is its form-factor. I did appreciate the physical keyboard, but I felt it also came at the cost of a weightier-than-necessary device and blocky form-factor (the Palm Pre had a sliding physical keyboard, too, and yet its designers managed to keep it fairly light). This may be a benefit to people who prefer to carry a physically substantial phone. I am not one of them.
The HTC Droid Eris shares many of the same benefits of the Verizon Droid. It is also lighter, and I didn’t mind relying only on a virtual keyboard—although that could be an insurmountable problem for some users. The one major drawback to the Droid Eris was that trackball, which was annoying and made some functions decidedly un-user-friendly; but future editions of the device may take a page from RIM and adopt a trackpad. At $99 after rebate, as opposed to $199.99 for the Droid, the Droid Eris may present a better price proposition for some users, depending on their data-plan.
In my own opinion, I declare a three-way draw between the Verizon Droid, HTC Droid Eris and the iPhone—but the next generation of the latter two devices could very well overrun Apple, unless Steve Jobs has something particularly innovative up his turtleneck’s sleeve.