I'm a very (and I do mean VERY) amateur web-designer / coder and cannot even imagine everything that went into this. From what I see 95% of it WORKS.
That's not just a "good job" for a site of this magnitude, it's a "fantastic job". Are there things I don't like? Sure. Mostly because I can't do things *exactly* the way I did it on the Classic site or because the new site seems to be geared more toward mobile devices.
I literally hate pop-ups...that's me personally. Plenty of people don't mind pop-ups and even find them convenient. I also find it incredibly annoying that the new site loads pages substantially slower for me. Others have reported the new site is faster for them.
Are there things I do like? You betcha! The ability to add multiple photos to the same memorial. The ability to change the photo category (from grave to person, etc.).
The ability to search and sort edits. Do I think they should have had more "user input" in the design phase? Absolutely!
Most of the "issues" I have are because the designers are NOT regular and/or heavy users of the site like we are. I believe if we objectively evaluate the site, it's not as bad as everyone makes it out to be - because we're judging it based on familiarity.
Product or Service Mentioned: Find A Grave Website.