The Fujifilm GF 30mm f/3.5 R WR complements the petite Fujifilm GF 50mm f/3.5 R LM WR for an outstanding kit for all-around use. In 35mm terms, they are equivalent in field of view to a 25mm and 40mm respectively. With these two lenses you can do a lot.
I much prefer the primes over the zooms in the GF lens lineup. I’d like to also own the 23/4 and the 80/1.7 (or 110/2) but that will have to wait (budget). And of course the superlative Fujifilm GF 250mm f/4 (sharpest lens in the entire line) along with the FUJIFILM GF 1.4X TC WR Teleconverter.
The 30/3.5 is very close to the Fujifilm GF 45mm f/2.8 in size and a few grams heavier. The 45/2.8 is an excellent lens, but I think a 30mm and a 50mm pair up a better than a 30mm and 45mm. And if the Fujifilm GF 80mm f/1.7 is added, then having 30/50/80 is a bit better spacing than 30/45/80. Still, it’s a minor difference, so go with the 45/2.8 if you want the speed.
However, the 50/3.5 is so compact and pleasant to carry that I encourage all GFX shooters to try the 50/3.5—you might really like the form factor.
Fujifilm badly needs a wider prime lens, but perhaps the Venus Optics Laowa 17mm f/4 GFX Zero-D will serve—I haven’t tested it however.
Bummer that Fujifilm did not design the 30/3.5 and 50/3.5 to share the same filter size.