I haven't used these myself, but I've read a number of warnings about retrofitting a headlight designed for halogen bulbs with HID. If the light source isn't in exactly the same spot as the filament in a standard H4, the light pattern will be off and likely a nuisance to other drivers.
Another issue is using HID for the high beam as well. If it uses a separate arc (rather than moving the bulb as some do), you won't be able to "flash to pass" since it takes a few moments for the arc to fire up.
As far as color temperature goes, the bluer lights (5000K and above) seem brighter, but actually do not improve vision over daylight-color bulbs. Stick with the neutral 4300K, unless you do a lot of riding in inclement weather -- then the yellow might actually help. And IMHO it's better for conspicuity if your headlights and aux lights are not exactly the same color, that way they stand out more.
2010 Triumph Tiger 1050se
2009 DL650A - sold
2005 DL650 - dearly departed
"I am enthusiastic over humanity's extraordinary and sometimes very timely ingenuities. If you are in a shipwreck and all the boats are gone, a piano top buoyant enough to keep you afloat that comes along makes a fortuitous life preserver. But this is not to say that the best way to design a life preserver is in the form of a piano top. I think we are clinging to a great many piano tops in accepting yesterday's fortuitous contrivings as constituting the only means for solving a given problem." - R. Buckminster Fuller