I think so yeah. Mine was free which makes it even better, lol, but I'd say it was worthwhile. You can calculate the vpd just looking at a vpd chart, but the fact that it tells you outright makes it easy to glance and make sure you're at an optimal place.
Girls coming along well, just taking ages. Both dwc plants got a root or two in soup, so won't be terribly long till they explode.
Also I quit posting on that thread bc every time I turn around someone was asking a silly question about 10ppm or wanted to know how to do something then would fuss about not having the time. Gets annoying lol