Colin Powell has decided to endorse Barak Obama and you can watch that endorsement here:
In summary, he thinks Barak Obama would be the type of president we need now, and John McCain would be too polarizing, especially since Sarah Palin represents an even harder track to the right.
Colin feels Barak is steady, made a good V.P. pick, has both style and substance, takes a broader approach that includes small towns and big towns, and shows vigor.
As endorsements go it is reflective and direct, like Powell himself. I don't know how much weight his opinions have with fellow Republicans, but anyone that wants to know his views has them in unambiguous form.