This is a question that is on everyone’s mind.  Below are a few reasons as to why you should buy an iPhone

• The new retina display is awesome.  Since you end up doing a lot of reading on the iPhone the new display makes this easier on the eyes.
• New processor and better battery.  Even if you have an existing 3GS phone this could be a nice selling point to upgrade.  While I don’t notice that much of a difference when it comes to the processor, I do notice a difference on the battery.
• The new iPhone 4 has the ability to record 720p video at 30 fps.  With this ability to shoot HD video, this could easily replace HD Flip cameras.  Grab the new iMovie app and things can get really exciting.
• New hardware design.  This phone is a lot thinner than the current 3G and 3GS phones and is more industrial.  The front and back are made of glass that is supposed to be 30 times stronger than plastic.  The frame is made of steel rather than plastic and should help with the durability of the phone.  I really like the feel of this phone over my 3GS and it just looks awesome.

So while all of these are great reasons to own the new iPhone 4 I am now going to play devils advocate and list some reasons as to why you may want to hold off on getting the new iPhone 4:

• If you are a current iPhone 3GS owner then you will already have access to some of the best new features of the iPhone 4 since some features are actually part of the new iPhone operating system they are calling iOS 4.  Multitasking, folder organizations, iBooks update, 5x digital zoom, home screen wallpaper, unified inbox, and over 100 other enhancements.  This update is available to you free of charge.
• No Verizon announcement, and if you want the iPhone you need AT&T.  Now while I have always tried to stay away from the cell phone provider debate, I know some people feel very strong about their hatred for AT&T, so this could be a big issue for you.  If that is the case it sounds like you will need to wait a bit longer for the iPhone to come to VZW.
• No more unlimited data.  AT&T recently announced that they were dropping their unlimited data plan option.  This means that you will have to pay for either 200MB or 2GB worth of data.  With the Netflix announcement at the keynote, the thought of streaming 2GB of data is a reality if you take advantage of that service.  Add on streaming radio and it won’t take you long to reach those limits.
• Lack of Google integration.  The fact that you can’t use Google Latitude or the Google Mobile features where you get turn by turn navigation for free is frustrating when you see all of your Droid friends using those products.
• Reception issues are pretty common.  A downfall to the redesign is the fact that the antenna is around the edge of the phone and when held a certain way you can lose your signal.  If you are a person that will end up putting your phone in some sort of case then this is a non issue, but if you go case-less then this is something to take into consideration.

I ended up ditching my iPhone 3GS for the iPhone 4 and so far I have been pretty happy with the device.  The camera, new retina display, the new OS, and battery life all make the upgrade worth it.  It even made my wife happy as she got to upgrade from the 3G to the 3GS, but she doesn’t know what she is missing….