The main reasons I upgraded from my 3GS to iPhone 4:

• Retina display
• Better battery life
• Better camera

Retina

The display is stunning – it is crystal clear and the colors are beautiful. Most apps simply become more crisp (assuming they don’t use a lot of low-res images). I don’t think you’ll see a ton of difference in the way you use apps due to the display, but you’ll enjoy the experience much more and it’ll feel less like a computer screen. This is one of those things where the old technology got the job done just fine, but man, after using this display for a few days now, I can’t wait to see it come to iPad and to traditional computer monitors. Once you get used to retina, all other displays start looking really blurry.

Battery Life

It’s excellent. It still isn’t going to last nearly as long as the iPad, but it seems to last significantly longer than my 3GS did while performing the same tasks.

Camera

For still photography, the camera seems to be improved, but it’s significantly better at low light photography. This is partly due to the new sensor technology, but it’s also due to the inclusion of a small LED flash. Don’t get me wrong, the low light photos are terrible compared to a DSLR or even a mid-range Point & Shoot…but it’s a huge step up from the camera in the 3GS that was barely usable in lower light conditions. Daylight photos (particularly macro type shots) range from good to excellent. If you want proof, check out this shot by a friend of mine. I’d say that under optimal conditions, the iPhone 4’s still camera is very competitive with mid-range Point & Shoot cameras. As for video, it’s 720p in size, but don’t expect anything close to Bluray quality. I put a couple of videos on my Vimeo account…these are “worst case” shots – indoors with low light shooting a dark subject with some fast movement. Quality wise, the video function alone is right there with my Creative Vado…there is absolutely no reason to use a Vado, Flip, etc. if you have an iPhone 4. In fact, when you add on the software (iMovie or otherwise), the iPhone 4 blows those devices out of the water.

Overall Feel

Compared to my 3GS, the iPhone 4 feels better & worse. I love the new design – it’s more sleek and feels even more solid. The downside is I feel more paranoid that I’m going to drop it. With the 3GS, you could drop it and have a pretty good chance of only minor scratches or maybe a small crack in the plastic back. With the iPhone 4, you’re either going to damage the glass on the front or back (and the camera is integrated into that back glass as well) or you’re going to bang up the antennas (since they form the metal band around the outside). In theory, the glass is super strong and not easy to break, but something about it just feels a little more fragile. Speed wise, everything feels fast. If you’ve used an iPad, it’s pretty much the same. I really don’t notice a ton of speed increase over my 3GS for day to day activities – I do know it’s much more powerful though, so I’m sure future apps will widen this gap.

FaceTime

FaceTime is the video calling feature built-in to each iPhone 4. I tried it out with a friend from Twitter and it’s certainly a nifty feature. It works as easily as Apple advertises…call someone, touch a button, and boom – video call. The big gotcha (for now) is that both parties must have iPhone 4s AND be on a WiFi network. I’m not sure I’ll be using this feature all that much, but I also prefer e-mail/twitter/IM to phone calls anyway. I can see it being pretty popular for some people and I do see a few use cases for myself.

iBooks

iBooks is an app I use a ton on my iPad. I was hoping the retina display would make it more readable to me on the iPhone 4. Text & images looks absolutely fantastic – but at the end of the day, I just can’t read on such a tiny screen. It’s not that the font is too small – I can see it fine – I just can’t fit enough content on the screen for my tastes. I read mostly technical (or at least non-fiction books) though, so books with less structured content may be a bit better. Imagine reading the tiny bibles you used to find in hotels – that’s what it’s like reading on the iPhone 4…super crisp text, but a little bitty reading surface. I do like having the ability to look up something in iBooks in an emergency though – so I’ll keep it installed just in case.

Multitasking

A lot of people have been anxiously awaiting multitasking on iPhone. I’m not one of them. I would like a few apps to be able to update in the background (Twitter for example) and I’d like to have a live IM client, but that’s about it. I don’t use Skype or Pandora on the phone, but if I did, I’d be happy. For me, this is a nice feature, but the only real benefit I get is that it’s slightly faster to switch between applications. Maybe I’ll be wow’d with what people are able to do with this in the future, but for now, I just don’t see much benefit for the tasks I do today…but I was never the target of this feature in the first place.

Reception

You’ve probably heard about the reception issues with iPhone 4. Steve Jobs said they don’t exist, but if they did, it’s because you’re holding it the wrong way. Apple corporate said they exist on all phones and you should buy a case. Well, they definitely do exist and I’m holding my phone the same way I’ve held every Apple iPhone. I’m going to end up buying a case I’m sure, but I’m really disappointed in Apple over this one. If you hold the phone in your left hand, you’ll connect two of the antennas with your finger or palm. By doing this, your 5 bars of full signal will drop to “No Service” within 30 seconds or so unless you happen to be very close to a cell tower. At home, I can do this easily every time I try. In West Knoxville, I had a harder time getting the signal to drop…so it seems to be partially dependent on your proximity to cell towers. I have yet to have a call drop due to this, but I have had SMS messages and data downloads stop/fail due to it…so it isn’t just a display issue – it really is losing the signal. Apple says some type of fix is on the way and if that’s the case, then maybe this won’t be a problem much longer. I expected I would get better reception than my 3GS due to the larger exposed antenna, but so far, my 3GS had a more stable signal. Call quality is as good or better on the iPhone 4 though. I haven’t tried making a call from a noisy area yet, but all of the calls I’ve made have sounded very clear on my end and no complaints from those that I’ve called.