I'm very sceptical in regards to screen cap comparisons as they aren't always representative of what the film looks in motion. If I don't own the disc myself or have viewed it on my personal equipment with my own eyes then I can't really comment on a transfer - I'd feel ill informed doing so.
Everyone has their own standards of what is 'acceptable' quality, but I do get the impression that a lot of Blu-ray fans are overly critical of presentations. I think it comes with a lot of these companies now putting themselves out there for all the world to see (and criticise), combined with higher expectations of the technology we have now in respect to picture quality. It's easy to forget that without these smaller niche labels releasing films like these, we probably wouldn't have them available at all - that's not to say we have to accept a shoddy transfer and like it, but sometimes the budgets and source materials just aren't there for these companies to go the extra mile in producing what some fans consider a fantastic master.
Having said all this, I don't own any the above SF titles so can't comment!
However, the ones I do have look good to me. I do generally prefer waiting on SF titles though to see if Arrow or certain other UK labels get them instead as I just prefer the overall package to SF's and generally speaking know that Arrow will usually do a better job.