  We present the results of new time series photometric observations of 29
pre-white dwarf stars of PG 1159 spectral type, carried out in the years
2014-2022. For the majority of stars, a median noise level in Fourier amplitude
spectra of 0.5-1.0 mmag was achieved. This allowed the detection of pulsations
in the central star of planetary nebula Abell 72, consistent with g-modes
excited in GW Vir stars, and variability in RX J0122.9-7521 that could be due
to pulsations, binarity or rotation. For the remaining stars from the sample
that were not observed to vary, we placed upper limits for variability. After
combination with literature data, our results place the fraction of pulsating
PG 1159 stars within the GW Vir instability strip at 36%. An updated list of
all known PG 1159 stars is provided, containing astrometric measurements from
the recent Gaia DR3 data, as well as information on physical parameters,
variability, and nitrogen content. Those data are used to calculate
luminosities for all PG 1159 stars to place the whole sample on the theoretical
Hertzsprung-Russell diagram for the first time in that way. The pulsating stars
are discussed as a group, and arguments are given that the traditional
separation of GW Vir pulsators in "DOV" and "PNNV" stars is misleading and
should not be used.
