I moderate the Strobist group on Flickr and, as a result, see a huge number of flash-lit photos (and kick a large number of non-flash-lit photos...). Over the past year or so I've seen quite a lot of photos (from amateur photographers) combining flash with continuous sources. These are very occasionally TH, occasionally fluorescents but more often nowadays small-panel LEDs. They work, but the continuous sources are nearly always used as extra lights for added colour from the sides, or for hair lights, or for lighting the backgrounds, or whatever - never, as far as I can remember, as the main source of light.
To my mind combining flash with continuous lighting in a studio setting when photographing people is something that makes sense only if those specific lights are all you have. That is, if you basically have no choice.
To an appreciable extent you lose many of the benefits of using flash (stopping action, low ISO, consistent and accurate colour rendering, choice of modifiers, huge range of variable power, not blinding your subjects), and you also lose the benefits (such as they are) of using continuous sources (basically just WYSIWYG).
From what you say it seems that you are quite familiar with using flash. Why, exactly, do you want to use continuous sources? Is there anything about them that would work in your favour apart from WYSIWYG?
18 to go... ;-)