I've tried the X-Lab Saddle Wing and hated it. Every bump in the road seemed to eject my bottles. I think I used it twice and retired it. Im not sure how the Flatwing is with the bottle ejection issue since it sit lower and the bottles are at an angle. Currently I have the AeroDrink and use the rubber bands it came with. I agree the rattling did get on my nerves too. I put an extra peice of bar tape on the aerobars where htey came in contact with the bottle. On my long rides I typically carry an extra bottle filled with my nutrition and dump it into the AeroDrink when it is empty. I am still trying to figure a good way to store and atach spare tubes/CO2 etc needed for my IM in June. That is the one thing that the X-Lab products had going for them.
JVic