1. A programmable logic device (PLD), comprising: a plurality of programmable logic blocks (PLBs); and at least first and second logic cells within at least one of the plurality of PLBs, each logic cell comprising a lookup table (LUT) and associated mode logic configured to receive a LUT output signal from the LUT, wherein: the associated mode logic is configured to use a single physical output port to provide a logic cell output signal from its respective logic cell corresponding to an operational mode selected from a logic function operational mode, a ripple arithmetic operational mode, and an extended logic function operational mode; and the associated mode logic for at least one of the first and second logic cells is configured to provide the LUT output signal as the logic cell output signal when the selected operational mode for its respective logic cell comprises the logic function operational mode.