well, it's out in the wild now -- ie7 has been released. you can read dean's (gm for IE) note on the IEBlog regarding the release.
now that it is out -- and likely windows update people will start downloading it, there may be some adjustments that sites may want to consider. why? because even in ie7 we are more standards compliant to the point that ie7 may break some of the hacks you had to do in ie6 browsers, etc.
to understand more about ie7 development here are some resources:
two great places to get some knowledge...and as always, the IEBlog is listening...