I finished the build over the weekend. Unfortunately I have some small health problems that are keeping me from doing any serious riding right now so I haven't been able to fully test it out beyond a couple small 2-4 mile rides around town. So far I don't have any thoughts on how stiff it is or is not. It feels bumpy because I used the 25c tires I've had lying around for over a year (I'm pretty devoted to 32c tires). When I can do more riding I think I will test it with a different wheelset that has wider tires because 25c feels hella squirrely to me. I'll try to do a better review on how it rides after I've been able to get some solid miles on it, but that might might still be several months down the line.
The bike does have some odd things that might be nice for ICAN to change in future versions: 1) The radius at the tip of the fork, around where the thru axle threads in, is really small. Small to the point that the heads of most thru axles will stick out a bit around the edge ever so slightly. It would be nicer if it was designed in a away that the thru axle could sit flush inside an indent like the rear one does. Plus its weird that the front/rear axles have different thread pitches.
2) Specific to me as a rider: I have semi-collapsed arches that cause my knees to go inward slightly when I pedal and its pretty common that my knees will brush against the top tube which feels extra weird because of how sharp the angle is on this frame's particularly flat toptube.
3) They did not include a chainstay protector which is not the worst but would have been nice to have.
4) Not a fan of the carbon cradle on the seatpost. I swapped it with a metal one from a seatpost that was lying around at home.
5) There is no Di2 specific hole for a rear derailleur, you have to use the one indented for mechanical drivetrains. I used a zip-tie to hold the cable down to the chainstay which does not looks all that elegant but mostly works (there are separate Di2 and mechanical holes for a front derailleur.)
6) Nothing on the frame was faced.
7) The whole issue with the stripped threads on the fork.
Things I do like:1) Looks super neat
2) Frame seemed very clean inside, it was easy to route the hydraulic hoses and Di2 cables. Other than the issue with the fork threads, building it was a breeze.
3) T47bb is definitely superior to BSA.
4) I like the geometry, especially the bigger headtube. Most bikes my size have a 120-130mm headtube, this one is 144mm. If slamming your stem makes you feel cool, more folks could probably do that with this frame.
5) The UDH is nice.
6) Big tire clearance. I put on a wheelset with 32C tires and there is still plenty of room, I bet you could fit 35c if you really wanted to go all out.
7) I put this as a pro because it was a fun side project for me and a humble bragging point - I got to design and 3d print the top and bottom spacers for the headset. I had injection molded parts I could have used but the OD of the headtube was 57mm and I think the bottom spacer that came with the barstem was 56mm. It looked a little weird. The mating features on the top spacer that came with the barstem didn't really fit them right either (these were the bars that came with the Onirii One frameset I built earlier this year - they are not from ICAN).
ICAN sent me a new front thru axle but the tracking they gave me has not updated in 10 days so who knows where it is. Right now I am using the front axle from my gravel bike which is a couple mm short (another reason not to do any serious riding on it yet).
It seems like a fine bike and it does look great. It was cloudy when I took the photos so they mostly don't do the paint job justice but it looks beautiful in the sun. I built it 1x because I had 1x chainrings I needed to do something with. It has a 42t front chainring and a 11-42t cassette so it has that 1:1 great ratio that is nice for a climby bike. The top end is limited though. One of those gearing calculators told me that it would top out around 33mph (at 110rpm). It's a slightly weird build and definitely not a race bike but I figure its an excellent bike for a climbing enthusiast that is not crazy about dare-devil descending or doing huge watts on the flats. It could be good for a climby road race with a hilltop finish I suppose. Plus you can build yours however you want