[T^2]

Our experience with the Vexpro products:

Ball shifter gearboxes
Pros: Compact, light, and in our experience they shift more quickly than dog clutch shifters. They were also easier to mount than the AM Shifters we used last year.
Cons: The output shaft came out! Please fix this. We had to pin our shafts (through a hardened steel shaft housing, mind you) to prevent this from happening. It would be great if IFI could implement a mechanical connection between the steel housing and the hex shaft that would be removable so we could swap out shafts of different lengths. One of our steel shaft housings also had a hairline fracture on it, but this seems to be an anomaly. The encoder gear press fit is not very good, and eventually it was so slippy in the shaft that we couldn't use it without supergluing it in. Finally, it would be nice if we could have different spreads that outputted at appropriate speeds. The way they are now, the output speed is only appropriate for direct-driving very small wheels, without a third stage.

Motors
Mini-CIMs are awesome. BAG motors work pretty well (we didn't have failures with ours like some other teams did), but I wish they were a bit more powerful, perhaps on par with a 550. Side note: if you stall a BAG motor for a really long time, as we did in Madera, it'll burn out and smell as bad as anything you've ever smelled in your life. Sort of a sickly sweet fruity vomit smell.

VersaPlanetaries
Pros: Very easy to adapt motors of all types, even CIMs and Mini-CIMs if you need to. Swapping out gear ratios is very easy, as is swapping output shafts. We're never going back to BaneBots planetaries.
Cons: It's so hard to get 550s concentric! I know there's some play in the face plate mounting holes, but it doesn't work amazingly well. It shouldn't be that hard for IFI to include a plastic or aluminum centering ring with the gearboxes, like some teams have made themselves. Also, it would be nice to be able to put a CIM or Mini-CIM on a planetary without butchering it.

Gears, Bearings, and Shaft Collars
Flipping fantastic.

Shafts
Pros: They work well, when they work.
Cons: They're so bent, all the time. Out of five 3/8" shafts we received today, only two were within a straightness tolerance that we could use. This is fairly representative of all the shafts we bought during build season.
The 1/2" shafts are better, but not too much better -- one of three shafts we received today was bowed noticeably. We would happily buy 18" long shafts (12" might be too short for many purposes) if they were straighter.

Pneumatics
Can you also supply single-ended solenoid valves, please? Everything else is great, and easy to purchase.

VersaWheels
(Disclaimer: we didn't use these on our robot; only bought 1 with hubs for testing, so take this with a grain of salt. I also can't speak to durability over a season.)
Pros: Very cheap, easy to put together, and grips very well...
Cons: In one direction. When pushed from the side, the wheel slides without much resistance. Given that when we play defense, we often block with the side of our robot, this is an issue. Perhaps this could be helped by offsetting the W pattern like so:
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Of course, this would probably make the wheel more expensive.