You would have thought Canon would have given these lenses STM, to make them properly video-friendly.
On the 650D... Notice the STM lenses were announced at the same time as the 650D, and although the 24 & 28 IS are just arriving in shops now, they were announced a while back.
At these prices they are niche products, and as such I think perhaps it will higher level video users who are buying them, if indeed video users go for them at all (faster primes seem to be the thing... plenty of solutions to stability out there already) and such high end video users will be using MF, and will prefer lenses with mechanical long-throw, tactile focus rings which have end stops.
AF & video - for serious use - is generally a no-no (you would struggle to find an ENG or PL lens with AF) especially combined with the additonal accuracy that large sensor cameras with their reduced DoF require.
Really the only complaint you can make about these lenses is the price. They are a great size, useful focal lengths, IS always a good thing, look to be well built, and USM. If these were $400-$500, everyone would be falling over each other to get one.
Unfortunately, price is everything. An easy pass for me, which is too bad because I would really like these lenses otherwise. I'll stick with my 28/1.8 which still costs $400-$500.
If at UK prices these were around £400-£500 then they would be a more viable proposition. I guess it's economies of scale. The obvious and extensive R&D that has went into these lenses is going to be recouped from quite a small user base. Do canon price them low to hopefully sell more, or do they price them with the assumption that if folk really need them they'll buy them? I don't the answer, just trying to figure the logic.
They are not fast enough for the focal length to give that shallow DoF look that everybody seems to be after (Samyang 24mm f1,4 may be genuinely better proposition for serious video users who shouldn't object too much to manual focus only and will positively embrace a manual iris ring)
I used to have a 28mm f2.8 non-IS, cheap, sharp, compact, and am currently deciding to go for either a canon 35mm f2.0 or a Samyang 35mm f1.4, just weighing up price difference and user experience difference. The 40mm f2.8 would be on there but I seriously object to the rip off UK price. I would sooner buy the voigtlander f2.0...
The 28mm f1.8 just never seemed to make my list, be it the extra cost or the indifferent, sometimes downright poor reviews. Maybe as a video lens it makes a bit more sense where folk don't pixel peep and the attention is generally going to be towards the middle of the frame.