Well we DID IT ! Last week we ordered a Davinci JointVenture with a rear disk brake and a top to bottom paint fade (speed yellow to guards red). We liked the Comotion Speedster as well but the ICS was a definite advantage for us. Since I'm going to operate the controls I decided to go with the upgraded components on the JointVenture vs. In2ition ($850 more but frames are identical). I don't know if you all understand this, but the Davinci ICS (Independent Coasting System) has 4 "chainwheels" (really cogs) in front so the In2ition comes standard with bar-end shifters. To utilize brake-shifters, one MUST use Campy Ergo brifters because Ergo lets you have many front chainring positions, while the Shimano system will not work for more than 3 front chainrings. I prefer the Campy Ergo shifters any ways and have them on my single. Since this is the end of the season, we're hoping to get our bike in 2-3 weeks, and to still ride it this season. We're in the Chicago area, so we typically stop riding by the end of October.
As I said before, we rented a Comotion Breve in order to ride it a longer distance and to fairly compare to the 50 miles that we did on the Davinci In2ition. It was a good day and we felt strong so we ended up doing 100 miles on the Breve. Initially we were "turned off" by the Breve because the drive train was in very poor shape, but we adjusted and started enjoying it. It creaked a lot (for 1st 75 miles), but it eventually stopped creaking after we did some out of the saddle "tests" and I tightened a couple of chainring bolts. It also shifted poorly. But the most disappointing part was that the BB flexed so much that it was hitting the FD. (Dwan (at Comotion) had told me that the new Speedster frames were much improved over the Breve (approx 5 years old).) I did not like the handling all that much either. The bike had clearly been abused, and I told the shop owner that we would not have bought a Comotion if this were our only Comotion experience. We had ridden a new Speedster briefly so I knew that it was better overall and we had both liked the Speedster. During the ride we tried to ignore the poor condition of the Breve (and admittedly more flexible frame) and tried to concentrate on comparing the ICS to a standard tandem drive train. By the time we got to 80 miles and our rear-ends were getting sore, we started feeling
the coasting advantage of the ICS<g>. We also discovered that my wife didn't like to pedal continuously as long as I did (she coasts more) which was not noticed when we rode with ICS.
When we had taken our initial brief back-to-back rides on the Speedster and In2ition (and best priced Burley Rumba), we both liked the Speedster best (ride, handling, component quality, value), and were not sure about the advantages of the ICS. After we took the extended rides (in real-world conditions and hills) on the In2ition and Breve, we clearly preferred the Davinci bike, except for the cost. If you compare the Davinci In2ition and Comotion Speedster, I feel that you get more for your money with the Speedster. During the ride we tried to ignore the poor shape of the Breve and tried to compare the Speedster to the In2ition. I actually liked the handling of the In2ition as well or better (during long ride) than the Speedster and we both felt that the In2ition had a stiffer frame (dealer did not think that Davinci was stiffer). But we both felt that the In2ition was better for climbing and similar in comfort, except that I felt more through the handlebars. My wife volunteered that "we were faster" on the In2ition and I could not argue that. Not sure if the Breve frame flex or 700 wheels had an effect on this (In2ition has 26" wheels) or if it was terrain/conditions/body differences. We both felt that the 50 mile ride on the Davinci was necessary to really see the advantages, and that riding any standard tandem drive train after that was just not as good, for us.
More specifically, when you're tired it's really nice to just coast and readjust your rear-end with the Davinci ICS vs constantly having to call coasting. The down-side of the ICS is that the stoker has to constantly re-synch the pedals after either rider coasts, but my wife found this to be natural and not a problem. Since we're rookie tandemites, I'm not sure whether we really have to be in-synch all the time any ways. Since I didn't have to re-synch (except for a brief ride as a stoker with the Davinci rep) it became a non-issue for us. On steep hills or when you're hammering it is useful to be in-synch. I'm sure that it's mandatory when standing but we're not confident enough to do much standing at this point. We were surprised at how much speed we were able to generate when we both "pushed" on the Davinci, because the frame did not seem to loose much due to flex. Another down-side to ICS is that the stoker cannot feel if the captain is braking lightly or trying to reduce speed gradually, while that is automatic on a standard tandem. So the captain has to call braking for many circumstances. We felt that this would not be a problem after we gain some more experience with ICS.
From day 1, I was convinced that the ICS drivetrain was far superior for shifting and gear availability. We will be getting 4 front chaingrings (12, 18, 24, 30 tooth equivalent to 24, 36, 48, 60) and 9 rear cogs (11-28) which will give us 36 gears from 21 to 135 gear-inches with 26" wheels (can you believe that range). ALL 36 gears are usable because the front chainrings/cogs do not inhibit chainline angle, and the shifting is far superior to any normal crank/chainrings in front (6 tooth difference plus very small chainrings). Rear shifting is good as well. The Joint Venture uses Campy Chorus brifters and Racing-Triple FD and RD. There is an extra eccentric (3rd BB) and extra timing chain due to the ICS, so more adjustments will be needed.
I hope that this long post is not boring and useful to some of you. I felt that it would be useful to describe our experience and decision process for future reference and to bring closure to our original query. During our decision process I spent a lot of time reading previous tandem forum threads and this was invaluable in getting me up-to-speed on tandems. Thanks so much for all your prior contributions to this forum. This forum is a real goldmine of tandem knowledge. Speaking of goldmines, Mark Livingood's detailed and practical posts and his web site (TheTandemLink.com) is utterly unbelievable for the depth and breadth of tandem info. (e.g. link to "How to use Campy Ergo shifters with Shimano drivetrain" which explains how Davinci does this.) Thanks a bunch Mark !
Of course, we can't wait to get this tandem to see the paint job and to ride it !!!!!