Are you already interested in crash reports? I'm not sure, I just eagerly installed from the master branch to test the date and label writing to .sav.
If not, ignore this and sorry 😅

Writing the following data results in a crash on my platform 1 out of 3 times. If I use all the data and not just a tiny slice, it always crashes.
I'm not sure how to report details about crashes. R quits with a fatal error and Rstudio reloads, I don't get a message. If I turn debug on the function Rstudio crashes too and I can see from the Mac OS X reporting tools that it's a segfault, but I'm not sure whether that's now related to haven or RStudio.

widgets = structure(list(time_period = structure(NA_integer_, .Label = c("quaternary", 
    "neogene", "paleogene", "cretaceous", "jurassic", "triassic", 
    "permian", "carboniferous", "devonian", "silurian", "ordovician", 
    "cambrian"), class = "factor"), partner = NA_integer_), .Names = c("time_period", 
    "partner"), row.names = 1L, class = "data.frame")
haven::write_sav(widgets, "w.sav")

sessionInfo()
R version 3.3.0 (2016-05-03)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.11.4 (El Capitan)

Oh, also, this is more minor: when installing via devtools, it complained about missing build tools. Solution was to go to 3.3.0, so I was a bit confused by that (I had all build tools).