It has always been a tricky path to make your page listing in SERPs stand out based on something else except for unique and catchy copy. Making your title in ALL CAPS in one such quite questionable tactic discussed at WebmasterWorld forums.
One of the questions discussed is: Can capitalization really effect the rankings? Does Google give more weigh to ALL IN CAPS words (like words in bold)?
Officially Google states it doesn’t care about the case:
Search is always case insensitive. Searching for [ new york times ] is the same as searching for [ New York Times ].
However sometimes people do notice some fluctuation (I have personally never seen this myself, have you?).
Another question is what impact a page listing in ALL CAPS has on click-through and conversion: