Consider this another vote against putting HIDs in High Beams, but with a small caveat.
The main reasons they are not the best fit are because all HID lighting has a warmup period (usually 10-30 seconds or so, more noticeable off a cold start but always there to some degree - if you need a quick flash of light, like for signalling to pass, your lights will probably still be warming up while you need them) and the extreme brightness in a High Beam. You think people flash their lights at you for driving with your High Beams on when they're not necessary? High Beam HIDs will be overkill.
That being said, if you're doing rural/mountain/off-roading/driving anywhere there aren't really regular light sources, or if you're going to turn your High Beams on and leave them on for extended periods of time, then HIDs could work for you. They're just not great for regular city driving or how most people tend to use those lights.
~Robert