I finally received and installed my half downs yesterday. Initial assessment:
On normal roads their is very little difference between stock and the half downs. On interstate roads I can definitely feel expansion joints in the rear but it's only slight and not intolerable. For those that say there is no change in comfort over stock with the downs... well it's all relative and I am a little older.
Handling is definitely improved. I haven't done any aggressive driving but that will come. I'll get an alignment in a week or so and will report back on how it looks. These are all after pics.
2014 Lexus IS350 F-Sport Ultra White, Roja Red, ML, BSM, PCS, RC, VGRS, RSR Half Downs