Use an external
software such as
gippy (linux) or
polarcom (windows mac linux) for gps and
nmea display. Gippy may well become an integral/modular part of opencpn at some stage.
By the way, course speed and wp distance are all displayed, just play around with it a bit or consult the extensive
manual wiki
You can display grib files within opencpn, if you are however receiving
weather faxes you will have to view them with the appropriate software. I doubt you will find a chartplotter that can display those.
USB to
serial adaptors have been reported to
work although there can be driver issues in
linux. Do check for compatibility if you intend to use it with
linux. On windows this should be a simple driver install.
If you are aware of any specific
reliability problems with ais and opencpn, please state where you found this information and/or get the source to report it as a bug; there's no point hearsaying this around. The
core dev team (Dave or bdboat on this forum) are (is) extremely responsive in resolving bugs. I am not aware of any ais issues at this time.