Searching for "Phnom Kulen" gets no results here, so I'm gonna ask...

We have four days in Siem Reap at the end of November. I know I could probably spend all that time exploring Angkor, but I also know that my wife cannot - she'll be itching for a change, even if that change is same stuff different location.

Guidebook I have says to avoid Phnom Kulen calling the entry fee overpriced. The one thing keeping my eye here is that my wife is a waterfall fiend and it looks like there's a decent one here (though I can't say how impressive it'll be at the end of November).

Anyone been? Worth the small trek out of Siem Reap? If not, best bets for a small day trip out of town, we're probably willing to sacrifice wondrous-ness (not a word) for crowd avoidance - if that's even possible - as it'd be nice to get a quieter day somewhere in this trip.

Thanks in advance for any tips.