I know that compatibility with MS Excel is of the utmost priority but there are some things that Excel does badly. One concerns the ChiTest function, which doesn't ask for df but assumes that the observed and expected frequencies come from a contingency table rather than a GOF test. In a Goodness of Fit Test the df are often less than in a contingency table since one may have estimated the mean in preparing the data. So a function that simply returned the calculated Chi-Test value (not just the p-value as in ChiTest, an output that assumes the df) would add a lot of value and save a lot of leg work for those who use PM to do stats.
Whilst we are on the subject of new functions, I presume that PM 2010 will implement the new functions in Excel 2007. So to complement AVERAGEIF and AVERAGEIFS it would be really nice to have STDEVIF and STDEVIFS. I can't think why MS left these out of Excel.