This was the first year in the past four that I stayed up learning the entire night. In the last few years, I would nap from about 10:00 to 10:30 before getting up to learn the rest of the night. This year, thanks to the naps I had on Shabbos afternoon, my early evening nap was not necessary. Of course this makes me guilty of preparing on Shabbos for Sunday, a forbidden act. So, I imagine that any learning I did that night was probably worthless as it came about through an aveira.
In addition, this was the first Shavuous night that I can recall where I did not crack open a Gemara the entire evening. Just about the entire evening (aside from time I spent preparing the laining for Shacharis) was spent learning Hilchos Shabbos in the Chayei Adam. Of course, according to some, the fact that it wasn't Gemara doesn't really qualify it as learning* anyway, so it could just as easily be said that I spent the entire night just wasting my time.
I also found out from a prominent Rav in my community over Yom Tov that because I was not happy over Yom Tov, I am no different than someone who does not eat Matzah on Pesach, or sit in a sukkah on Succos and so on. In some ways, it's kind of sobering to think that my entire avoda on Yom Tov is worthless because I wasn't happy and fulfilling the mitzvah of "V'Samachta." It's as if I never kept Yom Tov at all.
* True story: in high school, I was told that learning Chumash (or any "easier" subject) when one could be learning Gemara is bittul Torah based on the halacha in Hilchos Purim which says that we are m'vatel Talmud Torah to listen to the megillah.