Yes, sure I would. Doesn't sound like a glossy DTP kind of document. The document size wouldn't be a problem. Ask on the groff list with more of a description of the kind of content and what you might be worried about. Books like _The C Programming Language_, W. Richards Stevens' _Unix Network Programming_, and others are examples of what can be done. http://troff.org/pubs.html
I have used LaTeX for 200+ page documents (various) in the past, so to your question, yes I would.
Handing it over to someone else to maintain is a different thing though. Products like InDesign or PageMaker or Word understand that this is what eventually happens in reality. So, the not-so-steep learning curves that WYSIWYG tools offer have won out in the end.
If the manual is written by techies, and maintained in-house like all those old Bell Labs manuals that used troff, then markup based typesetting is not such a pain, imho.
