I made the switch to the Nexus One because I was kind of tired of AT&T and Apple. My contract was up months ago, so I switch to T-Mobile, and I will agree that there is not as much 3G service, but I will get to that in a moment.
The Physical
The Nexus One does not look like an iPhone, but it looks just as gorgeous. The only complaint I have from the physical design is a lack of a silent button, but you can silent your phone in less than a second.
The Software
This is where the biggest difference is between the two phones, that and the specifications. This uses Android's latest OS (2.1). There is a lot of customization any user can do without rooting (aka jailbreaking). Again, there are not nearly as much applications, but the applications on the market are very useful. I can remember scrolling through hundreds of duplicated applications or pretty much spam applications in the App Store.
Verdict
I have had my phone for about a week, and it fits my needs a lot better than the iPhone did. Both phones are extremely good, and I am in no way saying the Nexus One is better than the iPhone. Let's be honest, no phone that can come out will be able to beat the iPhone, Apple has a well-established "ecosystem" for their phones -- Android does not. If you have the money to buy an unlocked version, I would give it a try.
Side Note
This is kind of funny, when I first got it I put my AT&T sim card so I could roam around with Edge for a little until I got my T-Mobile phone. My Dad also has an iPhone 3G, and we did a speed test in the browser (Edge vs 3G). Now this is not a fair test at all, so the results were hilarious. Before I tell you the results, we live in Shamong, NJ and there is a cell tower literally right across the street for AT&T. I loaded up the full version of Engadget on both phone (Nexus One with AT&T Edge and iPhone 3G with AT&T 3G). The Nexus One literally won every test in the browser, which is backwards. I am leaving the results up to poor 3G in my area, but Edge was extremely fast for AT&T where I live, I guess.
If anyone would like any pictures, or personal questions answered, I will subscribe to this thread and answer PMs.
Thanks,
Ethan