Just be aware that we're still in the transition period, going from standard to hi-def, and because of that, there is currently a limited amount of hi-def programming available and that a lot of the current equipment (mostly the tuner/set-top box, not the display) will be obsolete and will need to be replaced before the conversion is really complete.
There are two competing standards for Hi-Def DVDs coming out, so be ready for the format wars again (think: VHS vs Beta). Many Hi-Def TVs still have 0 or 1 HDMI input, when you're eventually going to want 3-6 of them. Analog outputs on video devices are going to start going away.
As long as you realize that Hi-Def is still evolving and that it isn't the mature technology that Standard-Def has been for the last 25 years or so, then you're fine. If you're looking to just buy a TV and have everything work perfectly and all in Hi-Def, you're heading for some frustration.
-Troy