- I don't think it gives me any more speed - if it does, it's negligible. (I had one stretch over 20 mph, but I was working for it with a heart rate over 160 bpm).
- It adds weight.
- It was a pain to put on and it's difficult to access the air valve now.
- It flares a bit by 2 or 3 of the screwholes which I'm sure doesn't improve the aerodynamics.
- It interferes with the rear brake (which is still usable but rubs, even after I adjusted it).
- I'm concerned about the screws working loose (I could buy extras and some Loctite, but...).
- It's fairly delicate - it already took a couple divots on the rim when I ran over a piece of metal today.
- On the plus side, it didn't seem to have too much sail effect laterally when trucks, etc., went by - I did feel a little sway a couple of times but winds were only 0-11 mph today. Not sure what it would do in higher winds.
Plus I got a friggin' flat on the front tire out on the road after running over said piece of metal (yeah, that's the big glitch about mile 17 - after which I just rode home slowly). At least I hadn't changed that tire for the new one yet.
I'll file off the divots and try it again Friday, but after that unless I have an impressive workout then I'm taking it off. Just not worth the uncertainty in how it will handle on race day (since I don't have an extra wheel I can swap out for it easily, and removing the cover itself is a big job involving the removal of the cassette).