First, there's no readme for SP2 CTP available yet.
Second, it's not final release of SP2 but CTP (pre-beta) so it shouldn't be used in production. You should be carefull even using it in development.
The EXE buit with SP2 may or may not run successfully with SP1 runtimes depending on what changes SP2 includes and your code. In general, I would not recomend doing so because it may introduce prodlems which very hard to track down.

>If end users are runnng with SP1 runtime files, will that run exe's compiled in SP2 without problems?
>I don't see this mentioned in the readme.
>