THANKS to cmjars and indirectly Nick from Doug Thorley for the help, without a couple of extra tips I'd still be working on removing the rear panel!
Removal of the stock unit is the hardest part in my book. Those darn heat shield screws are nearly impossible to remove without the right tool: a closed end wrench. Getting the new unit on isn't very hard.
One of the biggest differences is the weight reduction, the stock unit is very heavy and the DT is much, much lighter. I just came back from an initial run, the sound is a little louder than I'd prefer it to be inside the car. However after not owning a car with an aftermarket exhaust in over ten years it's probably just my age catching up to me. The car definitely feels peppier from take-off, and I also noticed response from 60-80 mph is quicker on the highway too. One thing I really liked was as you approach a stop you can now "hear" the car downshifting...
Overall I'm very happy with it, we'll see how it goes after a week and month of ownership.