I love IS. I wish my 17-40 had IS, and would pay a lot extra for it.
But these? Nah. I would want either a relatively cheaper f4 IS or a f1.4 and I'd go without IS assuming they had substantially better IQ than any of the zooms in this range.
I'm thinking they are primarily for video on a crop sensor.
Also no-one has really seemed to mention it, but 24 and 28mm seem really close together. Is this just becasue they were designed similarly, so canon thought 'what the heck, we might as well make both'?
Or is is more 24 is a well liked FL on FF and 28 is closer to 50mm on crop?
No next we should get a 50mm IS lens for FF video.