1) Browsers require their own version of the flash plug-in and you have to take this into account and warn those viewers, who do not have a flash plug-in, or one that is working correctly with the browser they are using.
2) Flash, as a rule, is not very SEO friendly. Other work arounds must be used to make the page rank better.
I'm not sure that the Flash map will reduce load time. The flash us maps that I have seen are at least 25K in size. I think the advantage of the Flash map is that it looks nicer and allows you to add extra info on hover.
Actually, Google can now see content in SWF files. However, it won't give your site the same SEO juice. If you want to pass page rank, you'll need to you traditional links.
[edited by: eelixduppy at 3:10 pm (utc) on Apr 25, 2011] [edit reason] removed specifics [/edit]