Here are my impressions and observations after spending two-weeks with my new iPhone4.

• Retina Display. Without a doubt, going forward, this is the standard against which all smartphones will be judged. The ‘Retina’ display is outstanding. Here’s a case where the marketing-speak about the human eye not being able to see the pixels is spot-on correct. When holding the iPhone4 at normal reading distance (between 6-12 inches), you simply do not perceive any pixels, all letters are crisp and smooth. To compare, I went back to an iPhone3G and iPhone3GS and the improvement is like night and day.
• Size. The iPhone4 is slightly slimmer than it’s predecessors and is comfortable to hold for long periods. Before I got a case for the unit, it was a bit tricky typing on the on-screen keyboard in portrait view, but other than that, it’s feels completely natural.
• Front-facing camera. Having tried to take self-portraits with my old iPhone3G and guessing where the snapshot button was and what the picture would look like, this is a great new feature. Sure, it’s not as high-quality as the rear camera, but it’s acceptable.
• Battery. Seems to hold a charge a bit longer than my iPhone3G, but I still charge it at least once a day. Could probably stretch it to every other day, but I don’t want to risk it.
• Voice commands. Part of the new iOS4, it works as advertised. REALLY appreciate that it works smoothly over bluetooth.
• Mutli-tasking. Honestly, I never really missed this feature on my iPhone3G, but it is handy to switch quickly between apps via fast-switching.
• Faster processor. For me personally, this is probably the biggest improvement over the iPhone3G. Everything is snappy. For example, when updating my 40 RSS Feeds via the NewsRack app, it now takes about 15-20 seconds where before it took about 90 seconds.
• Camera. The 5-megapixel camera is awesome. I’ve since sold my Canon PowerShot A590 and Flip Mino HD with no regrets. Two less devices to carry around in my backpack!
• Antenna issues. Unless you’ve been living under a rock, you’ve heard about the antenna issues with this device. I can confirm that if you hold (and squeeze) the outside edges where the 2 black lines are, you can reduce the signal strength. Fortunately, I never buy an expensive smartphone without getting a case or skin. I picked up an iFrogz case and haven’t had any antenna issues.
• Sans Case. The design is industrial and the heavy use of glass —front and back — is nice to look at, but for the 24 hours before I got my case, I was a bit paranoid about it slipping out of my hand. Unless you will only use this in a padded room with carpet, get a case or skin. The aforementioned iFrogz case is great.

Summary. This is something like my fifth or sixth smartphone and is far and away the best. If you’ve got an iPhone3G, this would be a recommended upgrade, but if you’ve got an iPhone3GS maybe not so much.

How about you? Any thoughts so far?