The advance since October 2002 is certainly impressive on its own merits, but pales when compared to the prior decline. The advance has not even retraced 38% of this decline and formed a rising price channel. As long as the lower trendline holds, the trend is firmly bullish and further strength is expected (as outlined above).
A failure to hold above 2000 AND a break below the May low at 1865 would be quite negative. At best, it would signal a retracement of the Oct-02 to Jan-04 advance. At worst, it would signal a continuation of the prior decline (5133 to 1108).