I would like to recommend that SPGetCurrentUser accept the webURL option to be able to prevent an extra call to SPGetCurrentSite().
Comments: Note that there's a check at the top of SPGetCurrentSite to see if we already have figured out the site. if(thisSite.length > 0) { return thisSite; } But you're right: it doesn't look at the webURL default. That change makes sense.
Comments: Note that there's a check at the top of SPGetCurrentSite to see if we already have figured out the site. if(thisSite.length > 0) { return thisSite; } But you're right: it doesn't look at the webURL default. That change makes sense.