it was actually the best holiday i have ever been on. macchu pichu is breathtaking, i just got goosebumps thinking about it. cusco is amaaaaazing, the markets and stuff are so interesting to look round. i would definitely recommend eating alpaca, and although i didn't try it i heard good things about guinea pig. buy a hat, just because. er.. oh, buy a crappy paperback history of peru/the incas while you're over there, they sell some awesome ones in the markets.
you WILL enjoy it.