Apple released the 2.0.1 iPhone firmware this evening, citing ‘bug fixes’ as the reason. It appears to have addressed the two annoyances I had in 2.0, namely the long wait you had to endure opening Contacts (down to 3 seconds from 9 for me) and the forced refresh of Safari when switching between open windows (not good for AJAX driven sites like Google Reader). General UI animation and transition seems smoother too, especially keyboard popup and entry.
UPDATE: The forced refresh bug has not been fixed…Perhaps Safari refreshes the page when switching to a tab if some predetermined time has elapsed.