I think what you're seeing when you first turn them on is the high beam pattern. There is some sort of shutter mechanism that switches the pattern between high and low rather than a separate bulb or separate filament that gets turned on independently, and this shutter takes a moment to move to the low beam position. Also, the color of HID illumination tends to be a little too far away from where your eyes are most sensitive (too "blue" vs kind of yellowish, or 6k vs 4k for the brighter halogens).
There are a couple of things you can do to get more useful forward lighting with the OE HIDs. One is to stagger the headlight aim with the passenger side headlight aimed just a little higher than the left. This lets each headlight do a better job of filling in any dark regions of the other. Plan on experimenting a little so you don't get the pattern too high (particularly on the driver side), but this should not take very many tries. The other thing is to run the fog lights as well, which gives you better close-in illumination. If those aren't aimed too high either, most traffic doesn't seem to care.
I have the HIDs in my 2008.
'08 GT/5MT (mine)
'10 Subaru Legacy 2.5GT/6MT (hers)
'01 Maxima 20AE/5MT (spare, my occasional winter driver)
'95 626/V6/5MT (still in the family but not at this address)