You all give the people asking the questions entirely too much credit.
@sweetangst: Don't you think that's just a little condescending?
And I feel changing the 2 values may not cause any problem since any other reference to the old URL in the database might only be to the files, which in any case would not change.
That is the precisely the problem...yes they would change! If you move wp-content from the subdirectory to root, then the url to the files stored in the uploads directory there would be changed. Also, any references included in the body of posts, pages, text widgets, etc. would also be broken.
Test it yourself. I assume you have a wp site. Dump your db and do a search/replace on your url...if your db is of any size at all, you will likely see hundreds of replacements...not just two in the options table.