Mind you, the iPhone was already pretty special but the 3G was going to be perfect. 3G networking would enable quicker network access and the GPS capability would allow you to navigate yourself out of places like Harrow a la Tom Tom style.
Now the first thing we need to understand is that the 3G capability is only as good as O2's 3G coverage in the area you're currently in. Now I've heard that O2's coverage isn't great hence I have found out that it hasn't really improved speed capability. On top of that, having 3G activated sucks the battery life out of your phone quicker than you can say 'O2's 3G coverage is shite'.
The built-in GPS function is pretty sweet if only it would find your current location sightly quicker. Traveling across London to my hockey game in Chelmsford last weekend I was trying to navigate my driver using the GPS on my iPhone but by the time it had narrowed down my current location we had found the M25 and were half way there. Super!
All in all the upgrade hasn't really made that much of a difference. The best bit is probably that the 3G version is a few millimeters slimmer and possibly a gram lighter.
So my verdict is...... it's definitely worth it!!