I had cracked my brand new iPhone 4s digitizer just 2 days after the complimentary 30 day insurance period from at&t. I had to get it fixed immediately because I couldn't spend one more day without siri.
Everything went surprisingly well. I'm now much more confident thanks to the in depth guide from ifixit.
Don't forget the dust screen from the back of the old digitizer(the on that covers the ear speaker)! I did, and didn't notice it until it was all put back together. You can cut it out with a hobby knife, cut the molded plastic not the screen it self. Also make sure you don't pinch your power/sleep button ribbon cable during reassembly. I forgot to connect mine and pinched it under the logic board. Not until I disassembled again did I realize why my power/sleep button wasn't working.