Like Jeff, I have plenty of access to good fishmongers, so don't do online. But if you are buying things like tuna (typically frozen at sea) and shrimp (the one thing I usually buy frozen) there is no reason that quality shouldn't be topnotch. I'd be a bit less confident about delicate things like sole being frozen, but I'd think you'd be safe with a place like Citarella or Browne's Trading (never ordered, but have shopped at each in person). If I didn't have access, I'd probably place test orders with Alaskan Seafood and Fulton St Market (I get their ads online a lot).
Oh, I guess techically I do order seafood, a couple of times a year I get sustainable American caviar from Kelley's Katch.
Like Jeff again, I do order steaks (and lamb) from Flannery a couple of times a year. And have been happy with a couple orders of hard to get cuts from Wild Fork (who has seafood come to think of it, never tried). Lobel's I'm sure is great (and likely pretty pricey).
As to Goldbelly, that is generally mostly prepared stuff from well-known restaurants, but they have the process down pat. I've used for gifts seveal times, seamless. And have gone to friends who had the Zahav lamb package, great.
So a long way to say "no, don't know anyone who has used Alaskan Seafood"
