I have a vague memory of pitching this book against the wall when I first read it, since at a certain point in the proceedings it becomes obvious that the book is a combination of some of Heinlein's best work (The Rolling Stones, The Moon Is A Harsh Mistress, and Time Enough for Love) and one of his worst works, The Number of the Beast. Sadly, at the time it seemed to me that instead of being 75% the former and 25% the latter, it was more like the other way around. :(
Still, this time I kept on sloggin', and in the end was only mildly disappointed. Most of the loose ends are wrapped up at the end, but the McGuffin that drives the plot through the entire novel is left hanging, and you never find out whether the protagonist manages to pull off the epic raid that the story has been building toward, or whether he and his team fail miserably. Maybe this question is answered in To Sail Beyond The Sunset, but while I'm no prude, I'm not terribly interested in skimming through Maureen Long's extended sex life to find out. I can stand not knowing.
When all is said and done, I'm glad I didn't pay good money to buy and read this back in the day. I'd have been even more pissed off.
*Shamelessly stolen from Filthy Pierre; this is the concluding line to his filksong "The Future History", which covers most of Heinlein's work.