I have had the chance to make two webquests in my short time at uni, and even though they are not aswonderful as the pro's, I am extremely proud of them. The time and effort that goes into creating one of these is huge.
However, when compared to a unit of work that HOC's and teachers design - is it really that much more work? Personally, I do not think so. The beginning of the 'old' way of devising a unit of work is fairly much the same as designing a webquest - outcomes, focus question, research, activities that meet the outcomes, designing worksheets and then delivering the unit. All but one part of this is similar - the engagement. We know that we now educate digital natives who are computer savvy, but that doesn't mean they are instantly engaged because there are computers involved.
Webquests need to engage the students from the word GO, so that they are focused and determined to get through the quest, to most importantly of all - the authentic destination. Allowing students to go out on the world wide web - even with the safety restrictions of the school intranet - is dangerous in itself. This type of 'webquest' is not a true webquest at all. Teachers need to find and research sites, then provide searching activities through questions and tasks that engage the student in higher order thinking. This is the type of thinking that out students need to do, thinking that enables them to look outside the square and deepen their knowledge of topics. True webquests do this.
I believe that the time and effort that go into creating these are worth every minute. Plus - they're always there for next year.....