I've just put in an Optima battery and it cranks so much slower. Probably 2-3 seconds on the first start compared to about 1 second w/ the OE from '99! Wonder why?

Do you mean the engine actually turns over more slowly, or that it cranks ok but just takes longer to start?
Are you sure the Optima came fully charged? If it is cranking more slowly, put a voltmeter on the battery. At rest/engine off it should read at least 12.5V, less than that and it isn't fully charged. While cranking the engine it should not go below about 10V.
Also if you haven't already done so, check the battery terminals inside and out for signs of corrosion, and clean them up if you find any.