Foods we eat now have been genetically modified for hundreds of years. Corn was originally only a couple of inches long but was modified to its current size.
Modern tomatoes are very different from earlier versions (that's why we have heirloom varieties). They have been modified to have longer shelf lives, tougher skins and to be more resistant to bruising.
Hogs have been modified to provide much leaner meats.
There is a difference between cross breeding and developing hybrids and going in and manually changing DNA at a molecular level or inserting dna that is not part of the species. I'm okay with the first (although I think we have bred all the flavor out of most of our food in search for prefect look, long life, and transportability) but I think we open ourselves up for problems when we start introducing foreign DNA into plants and animals or turning on and off different markers.