Npower Software's PowerBooleans plug-in for Max does a very nice job of generating quads from complex boolean operations similar as with trims and fillets. I have no idea how this is done algorithmically, but I found this promo page at turbo-squid: http://www.turbosquid.com/FullPreview/Index.cfm/ID/228190 (Login is required for the promo PDF) and this page at npower: http://npowersoftware.com/booleans/pboverview.htm (Bottom pic shows off quad boolean)