The minimum information on a landing page (eg take the bonus or bugger off) is probably based on the theory that you don't want to give people to many choices. This has been shown to be quite successful in other areas of online marketing. Of course, the essential piece to completing the puzzle is that you really need to pre-qualify the visitor before sending them. Really stress the bonus/game/etc and then send them to the landing page that is directly and only related to that particular bonus/game/etc.
By all means include a link to the casino's home page, bonus terms for those visitors that might want further information, you just don't want them to get distracted from the main message you used to send them to the page in the first page.
Back to the download issue, a casino's download page should never immediately initiate a download. It should be a page with brief details about the requirements for running the download. That said, I'd love to hear from a casino's point of view whether the automatic download option works. Perhaps it is like the popups in that everybody hates them, however, they continue to work.