I've bought some finecast sternguard and they were wonderful. No huge miscasts at all, just a little bubble on the side of the foot of one marine- easily coverable with basing materials. There were a few other very tinny bubbles but with paint on they're unnoticeable. The smaller details like all the little chains and icons are really crisp and really show. Not to mention they're so light and easy to glue together. Being resin convertable too.
There was quite a lot of flash though, but that is dead easy to remove. The smaller, thinner pieces like the slings on the guns feel very fragile, however that could just be me and they havn't broke, i was just worried they might not being metal.
Overall i'd say they are certainly worth it.