As one whose gone from an iPhone 3G to an iPhone 4 I can say the 4 is almost like a different phone. It's that much better.
I'm a little puzzled with your line of reasoning. You are unhappy with the iPhone 3G which is two generations old and you don't want to upgrade to the newest iPhone which is getting rave reviews but you will consider a new Android phone made by some unspecified company. Wouldn't you want to compare the iP4 to the Android platform phone?
It is not the hardware that bothers me, it is Apple's release of the software, for example:
iOS 3.1 Removed Tethering Support from iOS 3.0
iOS 4.0 Slowed Down iPhone 3G
iOS 4.1 Removed Notes to Gmail Sync Feature from iOS 4.0
iOS 4.2 Delayed 3 times from 12th, 16th, 22nd of November 2010, and still did not significantly restore the iPhone's usability to how it was originally.
It is great that Apple supports older hardware but am getting tired of being short changed all the time and with the iOS4 release, I just get the feeling that Apple is purposely forcing users to upgrade when some are already happy with what they have got before Apple released the updates.
You can simply opt not to upgrade the os, but Apple iPhone servers only signs the latest iOS release so if you had to do a restore your phone will be updated to the latest release. Also apps on the store will continue to get updated to support the latest release and will likely not behave properly with older OS. (My brother in law's 3.1.3 phone can't even open certain apps which have been iOS4 tested)
Perhaps Android has it's own issues too and we will have to see if the Nexus line will go through the same sort issues when future releases are available. (Non stock Android phones can't be compared directly with the iPhone for obvious reasons)
Also I was comparing on the platform as a whole and contemplating whether it would be a better option to move to Android since I use a lot of Google's services and I don't want to have to wait and wonder if Apple will implement them on their mobile platform, in eg Google Maps Navigation.
When I bought the iPhone 3G during that time, I wanted a phone which offered the best integration with my Mac in eg iCal, Address Book, iTunes, iPhoto, Aperture.
Today I want the added integration with Google's services beyond that which is offered by Google Sync on the iPhone and be able to use new Google tools rolled out on the mobile platform.
Having said that I understand the strengths of an iPhone as well and I am not sure if I can make the compromise of hoping on to another platform. For those who see the light as I do, it would definitely be a point to ponder with the future releases from both camps. Time will tell.