I noticed when I had my old crt next too my new 1080p 46" Mitsubishi LT-46131 LCD (I'm in the process of switching them out) that when I'm flipping through the DirecTV Guide there is a lag on the Mits (the selector/highlighter gets there faster on the crt). There is also a lag in the audio (things are said a tiny bit sooner on the crt).
Is this normal?

Will this be a problem when I get an Xbox 360? I love playing Halo (and a lot of other games) and I hate to think that my shiny new TV is ill suited for gaming. My primary use is watching TV shows though.

P.S. If it matters, this happens while watching standard definition through composite cables. DirecTV hasn't installed HD yet.

No one can offer advice?

You've just opened a MASSIVE can of worms. There's a long running thread that's been going on for (at this point) years, regarding this.

Go here to this thread (http://www.avsforum.com/avs-vb/showthread.php?t=558125) and read all about it.

The short answer is that your Xbox 360 will experience small degrees of lag. Things can be done to reduce this, such as matching the output resolution of the Xbox to your TV's native resolution, enabling "gaming mode" if your TV has it, and using a VGA cable for your Xbox.

This problem will only be a major factor if you play rhythm based games (DDR, Guitar Hero) or Sports games with "timing meters" such as the kickoff in Madden or the swing meter in golf games.

Most other games, you should be ok if you read the faq and take the necessary steps.

Or, if you're rich, you can drop around 2k to buy DVDO's expensive upscaler, which will eliminate 99% of the lag.

I never noticed the lag on my Samsung DLP until I tried to play Guitar Hero II on it. Samsung DLPs are supposedly one of the worst, if not the worst when it comes to lag. Halo should be fine for you. On that note, even though we use different brands, this should help. What I did was set the 360 to my TV's native resolution and enabled gaming mode. Even in Guitar Hero I don't notice the lag anymore.