I agree, do your research and decide what model best fits your needs.
I have a 2008 Tahoe - LT, not my daily driver as I basically drive it for long distance driving and when I need to transport larger items.
There's not a ton of electronics on it, so personally, I did not get any extended warranty.
I just bought a '09 Vette and drive it as my DD. It has a ton of electronics on it, so I did buy an extended warranty.
I don't really have a lot of experiences with the LTZ, which is the top model. If the Z55 auto ride suspension is an equivalent to the F55 option in my Vette, it is very expensive to replace. If the system goes out in my Vette, it's roughly around $3K to replace This option is commonly known as the "Magnetic Selective Ride Control System" or MSRC.
Here is a short explanation of the Z55 option, taken from this forum;
http://www.tahoeforum.com/showthread.php?t=3806