I'm afraid I'm only commenting on hearsay here, not actually firsthand experience. Because we still don't have Adobe Studio CS3 at work. Yes I know, a professional "New Media" agency doesn't have the latest and greatest software... shocking.
But anyway. People have been conversing / moaning / arguing on FlashCoders mailing list today, about how Flash CS3 weighs in at around 400mb and a 30min+ install time, compared to Flash 8's 110mb and less install time.
They're all worried that Flash could end up going down the road of Adobes' Acrobat in terms of file sizes and continual 'updates'. Heck, I use Foxit PDF Reader over Adobe Acrobat now, because every time I start Acrobat (when its' finished loading) it wants to download ~60mb of new updates (Version x.x.x.13) - each one requiring a full system reboot.
(One of) Flashs' benifits is the relatively small size for something so unilaterally powerful, and the ease of updates. If Flash turned out akin to Acrobats' bloatware, people wouldn't like it so much, and we'd be in trouble...
Come to think of it, Flex isn't too kind on the optimization front. File-size-wise, my own Web-based Induction Training weighs in at 223kb, whereas similar functionality Flex apps are at least 4x that, last time I checked. Ok, it is a completely custom Flash App from the ground-up, but I hoped Flexs' ActionScript 3.0 would be a little more impressive on the download-size front. Apollo / AIR apps are looking good though, let's just hope they stay thata way.
Anyway, I'm digressing...
Lets hope that it never becomes an issue.