I've spent the past two days over Christmas playing with the G1 powered by Android in depth. The phone is actually growing on me. The fact that it is powered by Google's android makes it fully integrated with all of Google products (gmail, calendar, gtalk, picasa web, etc.), this means very little configurations for a user and once you logged into your gmail account (assuming you have been taking advantages of all of Google's web services, you can have a pretty cool mobile experience and convenience over the G1. For those keeping multiple Gmail accounts, this could be a problem as G1 is only intended for one primary account. I've yet to figure out how to sign on to second or third Google account if you kept some of your web services under separate logins.
While I've mentioned that Android is not nearly as polished as latest iPhone firmware, it does have advantages over Apple's creation. For example, the phone itself is really software independent, no desktop sync software like iTunes is necessary to do anything to add songs, files, etc. Having cut and paste is also a plus. Marketplace is straight forward to use. Since the phone is multi-threaded, you can have background tasks going while doing something else. A good example is when I downloaded two or more apps simultaneously; while waiting, I was surfing the web and checking emails without any problems.
I think the G1 and Android is a remarkable smartphone, which by my definition is a phone capable of doing lots of things. And the G1 is doing a pretty good job in terms of specs and feature sets. When compared to the iPhone, it does lack the sex appeal. With Apple's core strength coming from its iPod origin, it makes it more inviting to explore the multimedia aspect whereas for the G1, I find it a chore to upload songs and movies to the SD Card. The lack of 3.5mm headset jack is a major turn off as I refuse to use the inferior headset that comes with the unit. I will continue to use the G1 for the weeks to come to provide more feedback.