it will at exp during gameplay but when you go back to the mission select area the added experience isn't factored in.
inb4PWizardsaysitdoesn'tworkincampaignmode
This option is meant for Skirmish mode only. It doesn't work in the campaign. But the Cheat Mod add exp option seems to work.
However be warned, advancing in places you should will leave you vulnerable to attacks. You may grow, the enemy will grow for sure, but not the items.
[Edited by AdmiralAckbar, 9/4/2010 3:24:59 PM]