From what I have understand (don't have these on yet but near future):
1. Band clamps are better than the U clamps that come with SD headers.
2. The gaskets that come with the headers are not great quality, so consider better ones.
3. Buy sealant regardless.
4. The SD header flex is bad, but you could use it until it fails. When replacing use a 3" interlock & braided flex only.
5. The SD headers have a U Bend, which is 3" and flows fine, but it will drag on the ground like a dachshunds nuts if you are not careful or if the car is lowered.
6. The headers package comes with sufficient tubing to replace the factory catalytic conv. This also elminates the factory U bend (not the headers U-bend). If you want to run a cat, consider buying a magnaflow 3" cat for $60. Headers can also mate to the stock cat, but the factory U bend is after the cat and should then be eliminated if not already done so.
Additional: Removing the factory catalytic modifications should be coupled to a reprogrammed PCM with provision for this (according to what I have read).
Hope this helps.