I have a Mac connected to my TV and stereo system (S-video cable and Xitel USB audio), so I USED to watch iTunes downloaded shows that way. But, in the last 6 months, iTunes and the m4v downloads have surpassed the processing power of my G4 Titanium laptop, so now I can only listen to my iTunes music through my stereo until I upgrade the Mac I use for my A/V stuff.
I wish I could burn iTunes shows to DVD, but obviously that doesn't work.
If you want to skip the Apple TV purchase, you might be able to directly wire your Mac into your TV, but obviously there are tons of logistical issues involved.
Good Luck,
Mark