No.
Theres a few major things missing like the hardware to accomplish all thats on the 3GS like better video camera, faster processor, more RAM, compass etc...
You wont get the same experience no matter how much you try to hack it. The speed alone its the best improvement out of them all IMO.
And with backrounder you can multitask programs without even breaking a sweat since its got plenty of RAM to handle it.