Players can go from hero to zero very quickly, especially in forums like this. His form has clearly dropped compared to his best seasons and football is a short-term business, so if it continues there is a decision to be made, particularly as we have a very good second keeper (but who apparently can't play regular first team) and Henderson in such good form.
I still contend it's too early to risk replacing him with Henderson, who is a great prospect but playing in a much more defensive setup. We could bring Henderson back and make him and De Gea fight it out, much as DDG had to with Lindegaard in his first two seasons. Henderson may well prefer regular first team football elsewhere. There would a question of what we do then with Romero, would we keep him as a keeper for cup tournaments (accepting his appearances will diminish anyway if we re-enter ECL), or use DDG and Henderson?
The statistics on his titles are irrelevant to his current form - most of his time here has been during years since SAF retired and we haven't been winning much. At times he's been our player of the month or the season, which speaks volumes about the people he's been playing with. In the case of the Spain team, he has likewise been playing in a team in decline and Casillas was the first-choice keeper during their most successful years.
At present I would stick with him, unless he performs disastrously in the remaining matches this season. Otherwise, assuming Henderson's loan to Sheffield Utd is renewed for next season, we would have to rotate him with Romero. I still think he's one of the best two keepers in the EPL, along with Allison, but the margin of difference is no longer as big, if you watch the performances of most of the other EPL keepers and that's where Roy Keane's "most overrated keeper" rant has a grain of truth in it.