There is a small change in toe, caster and probably camber when you lift the IFS. My before/after alignment results weren't radically different. My toe was slightly out of spec and corrected. My caster couldn't be corrected back to spec though--currently around 1 degree (spec is 2.3 to 3.8 degrees).
So, I won't say it's completely necessary to align it afterwards but if you just bought some new tires, I'd say its money well spent.
UPDATE: By only adjusting the AHC sensors for lift, you'll lost some load carrying capacity. In order to retain the load carrying capacity, you should crank the front T-bars a bit and adjust the sensors some. The vehicle's load is shared partially by the spring/T-bar and partially by the AHC system. Having the correct balance between the two will yield the highest capacity and best ride. In the rear, you should be adding a spring spacer and adjusting the sensor if you want stock load carrying capacity. For best results, you'll need a brake pressure tool to accurately adjust the sensors.
Adjusting just the sensors for lift is not a bad thing. The AHC suspension is taking on a higher percentage of the weight and the springs less weight. Not really a bad thing as that is exactly what happens when you push "H" on your suspension height.
For more load capacity, you'll need to replace the springs/t-bars for ones with a higher spring rate.