  We report on eight millisecond pulsars (MSPs) in binary systems discovered
with the Arecibo PALFA survey. Phase-coherent timing solutions derived from 2.5
to 5 years of observations carried out at Arecibo and Jodrell Bank
observatories are provided. PSR J1921+1929 is a 2.65-ms pulsar in a 39.6-day
orbit for which we detect $\gamma$-ray pulsations in archival Fermi data. PSR
J1928+1245 is a very low-mass-function system with an orbital period of 3.3
hours that belongs to the non-eclipsing black widow population. We also present
PSR J1932+1756, the longest-orbital-period (41.5 days) intermediate-mass binary
pulsar known to date. In light of the numerous discoveries of binary MSPs over
the past years, we characterize the Galactic distribution of known MSP binaries
in terms of binary class. Our results support and strengthen previous claims
that the scatter in the Galactic scale height distribution correlates inversely
with the binary mass function. We provide evidence of observational biases
against detecting the most recycled pulsars near the Galactic plane, which
overestimates the scale height of lighter systems. A possible bimodality in the
mass function of MSPs with massive white dwarfs is also reported.
