just converted my (105) 916 to a (ultegra) 918.
It is my daily commuter - hence the U-look bracket thing (too much of a pain to carry that separate).
How to upgrade from 105 8 speed to ultegra 9 speed... for free: wait until a smashing deal for a barely used ulgetra spec'ed bike shows up on CL (be patient). Must be cheap enough for you to resell for the same price with 105 8 speed - won't work for every bike. Pounce fast. Switch groups and sell for the price you bought it. free ultegra upgrade. easy as that. The 105 group was in perfect working order, i just wanted a 9 speed and a bike with ultegra came up first. It does still have the original 105 headset and FD though - will upgrade those in time (along with the pedals).
Tires were supposed to be orange. I ordered them online and they sent me yellow ones because orange was out of stock. ugh. Also still need to put bar tape back on.