the digitalDelay is a KILLER!!!! all you get is pictures of fish butts.
Strange, I've been shooting a C5050 for 2+ years, I seem to have gotten more than fish butts. I guess the delay is a killer if you're used to a DSLR already based on some people I've talked to. People I know who have gone from a PnS to a DSLR have always commented on how responsive the DSLR seems; I went from a Canon S50 to a C5050, I wasn't used to a DSLR, so delay wasn't a big deal to me. I get my share of fish butts, I just don't worry about it because its digital and it doesn't cost me anything to delete the picture, and I dive enought that I know I'll eventually get another chance at a shot.
I like my C5050, I think its a good camera, and there is something to be said for being able to wet mount lenses. If you get a TTL strobe and it can be reused with the F100, that could be a good way to go - you'll always have the C5050 as a backup once you finally get the underwater housing for the F100, and the C5050 package would have some reuse for you. If you're determined to get a housing for the F100, the real question is whether you have an immediate need to shoot something now, and how long it will take you to save for the F100. If you have a big trip next week, and don't have an underwater setup right now, go with the C5050. If you're just looking to shoot local stuff that you see all the time, how long do you have to wait, and how much longer will you have to wait if you buy the C5050? If you're worried about shot quality, I know I've labeled my shots that were taken with a C5050, Sea Yoda is a C5050 user, Alcina was and is(?), and how many others??? You can get excellent shots with a C5050, it just takes getting used to.
I say get an Oly8080 full setup...
One friend of mine is ditching his 8080, because he's seen my 5050 setup and thinks the 8080 is more trouble than its worth. He's looking to "downgrade" as it happens, and recently borrowed an A520 from me to go to the Caribbean. Just a for what its worth...I've seen excellent shots taken by my buddy with his 8080, he just thought it was bulky and a major hassle. It was bulkier than my Patima aluminum housing, but not quite as heavy, and the Olympus didn't allow for 67mm wet mount lenses. Of course, some people think the little point and shoots are too bulky - you're probably not one of those people if you're going for a DSLR housing.