I've recently posted his fights with Sam Greco and B.J. Penn, so I'm only going to post a few more so folks who may not be familiar with him can get a better idea.
Personally, my main concern is how Lyoto will handle Ortiz's physicality and wrestling. Machida has a very wide stance and while he's got excellent movement in and out of range - and Ortiz has a tendency to reach on his takedowns out of desperation, e.g. third round of his fight with Forrest Griffin - you have to think at some point (especially early on) Ortiz is going to get the takedown with some sort of snatch single or double. From there, we know Machida has a good guard and underrated BJJ, but Ortiz has an excellent base, vicious ground and pound and good submission defense. I see this fight going Ortiz's way early on with Machida doing well as the fight wears on. More fights after the jump.
Lyoto Machida vs. Stephan Bonnar
Lyoto Machida vs. Michael McDonald
Lyoto Machida vs. Rich Franklin Part 1
Lyoto Machida vs. Rich Franklin Part 2