The technical writer's wet dream looks like this:
"I've recently joined a startup company that has never had a techwriter and needs me to write all the doc from scratch."
Being a wet dream, this question has more that one right answer. However, as I managed not to send my reply to the group (one of the strongest YahooGroups features), I recall it here.
I'd go for constructing a writing culture from scratch. Having my documents reviewed by Markeing / PM / R&D is crucial for their quality. Writing in FrameMaker, PDFing the document and shipping it to R&D for a review, is actually saying "Please don't comment to this document. If you feel you must comment to it, a 'job well done' will do. Here, let me spell 'job well done' for you".
Writing in MS-Word, on the other hand, is far better. Tech Writers don't like Word for several good reasons. However, Word allows for tracking changes in a manner no other writing tool does. Having the document straight with all R&D comments taken care of is far more important than having an FM file nicley * transferred to WWP. **
Tech Writing is a customer facing business. Keeping that in mind makes happy customers. Happy customers make rich Writers.
* I know that 'nicely' is very generous here
** If you don't know what WWP is, count yor blessings