I love the iPhone 4...don't think I could use <3GS iPhones again lol.
Coming from someone who hated the new design from the first leaked photo...I have to say I love it! The Oleo-Coated glass is so smooth, the phone feels so comfortable to hold being so thin, and feels solid
All the buttons work fine and have a satisfying click
As soon as i powered it on....the retina display, wow
I did a comparison next to my iPad and it was amazing
The iPhone could zoom in on text more than the iPad and it was still incredibly sharp next to the iPad...and the thing is When i got the iPad, and was still using the 3GS...I was so pleased with the quality of the iPads screen. So that says how much of an improvement the retina display is. The only thing that bugs me is the apps that haven't been updated to display properly on the retina display but whatever 
I love the folders, multitasking in iOS4. I only have two folders. One for Utilities & Games. I'm too used to having to click the home button to go back to the main page and selecting an app, BUT i'm trying to remind myself that I now have multi-tasking
Its so easy to use and steve jobs was correct when he said that even though they were last...they done it best
I'm happy that ipad controls are still accessed via double home click and.....that we now have an option to lock screen rotation
The actual multitasking is great but the only problem is that I think it would probably just be quicker going to the home screen to open an app, instead of sliding the apps at the bottom to find the one you want. And if I'm in an app and I want to switch to one that I haven't used I find it quite annoying to have to go open it. Maybe its just me lol but i'm glad multitaskings here. Plus i can finally use my TuneIn Radio app in the background without having to have it open a stream in safari 
The camera another great new update on the iPhone is amazing. I'm glad we finally have 5mp camera on the iPhone. I've had a 5mp camera on my old samsung from 2007 which is worth £4. 5mp is perfect for smartphones. So any future updates to the camera wont tempt me. The higher the megapixel means the more photos you take the bigger the photo actually is, therefor taking up more space. 5mp is perfect. The flash is also a very welcome addition! It works perfect and makes dark photos look great. Its alot better than taking a dark dark photo and having to put it through a image app to brighten it up and stuff to be able to see a noisey picture of what you took. The HD camera is amazing too. Kinda makes me wish i didn't buy a 400£ HD camcorder lol. I love it.
The iPhone certainly is a lot faster. 512mb ram in the A4 chip
which brings it above the iPad
memory wise atleast! uses the same processor and has more memory
while the iphone 3gs was fast i'd say the iphone is double the speed, if not then even faster
However I was using an safari and it crashed twice...not sure what all that was about but apart from that hiccup it's been going strong
And even with all this power, the iphone has loads more battery life. Haven't really put it through its paces yet but i'm looking at double the battery life
So even if battery life does decrease when i use more cpu/date intensive apps I'm sure it'll still have a pretty good battery life
The other features. gyro/iads i haven't fully experience yet, but did find that it was much easier to control the car in a Real Racing (perhaps the gyro improved this) and the thing is...I didn't really enjoy racing games too much because i found it too hard to control the car, but found it enjoyable on the iphone 4. again not sure if this is due to the gyro.
iPhone is a solid, nice looking phone. Only thing i'd worry about physically is scratches or dropping it. All the hardware is amazing. the front facing camera, 5mp w/flash, HD camera is worth upgrading to. The gyroscope has potential, and the processor/memory is worth it too. iOS4 is a great update with folder/multitask etc Sure it won't be perfect there will be 4.x.x updates im sure but it's a massive improvement over 3.0. Obviously 4.0 is out on all iphones/itouch (cant wait for it to come to ipad!) so everyone can get a hold of it but If your not sure about the iPhone 4, and have the funds to get it....then get it
You won't be disappointed
Coming from someone who hated the new design from the first leaked photo...I have to say I love it! The Oleo-Coated glass is so smooth, the phone feels so comfortable to hold being so thin, and feels solid
As soon as i powered it on....the retina display, wow
I love the folders, multitasking in iOS4. I only have two folders. One for Utilities & Games. I'm too used to having to click the home button to go back to the main page and selecting an app, BUT i'm trying to remind myself that I now have multi-tasking
The camera another great new update on the iPhone is amazing. I'm glad we finally have 5mp camera on the iPhone. I've had a 5mp camera on my old samsung from 2007 which is worth £4. 5mp is perfect for smartphones. So any future updates to the camera wont tempt me. The higher the megapixel means the more photos you take the bigger the photo actually is, therefor taking up more space. 5mp is perfect. The flash is also a very welcome addition! It works perfect and makes dark photos look great. Its alot better than taking a dark dark photo and having to put it through a image app to brighten it up and stuff to be able to see a noisey picture of what you took. The HD camera is amazing too. Kinda makes me wish i didn't buy a 400£ HD camcorder lol. I love it.
The iPhone certainly is a lot faster. 512mb ram in the A4 chip
The other features. gyro/iads i haven't fully experience yet, but did find that it was much easier to control the car in a Real Racing (perhaps the gyro improved this) and the thing is...I didn't really enjoy racing games too much because i found it too hard to control the car, but found it enjoyable on the iphone 4. again not sure if this is due to the gyro.
iPhone is a solid, nice looking phone. Only thing i'd worry about physically is scratches or dropping it. All the hardware is amazing. the front facing camera, 5mp w/flash, HD camera is worth upgrading to. The gyroscope has potential, and the processor/memory is worth it too. iOS4 is a great update with folder/multitask etc Sure it won't be perfect there will be 4.x.x updates im sure but it's a massive improvement over 3.0. Obviously 4.0 is out on all iphones/itouch (cant wait for it to come to ipad!) so everyone can get a hold of it but If your not sure about the iPhone 4, and have the funds to get it....then get it
You won't be disappointed