Apologies for the double-post, but thought I'd ask here as well.
After playing with NextGen, it feels incredibly bloated and hard to use; it's like using a sledge-hammer to nail in a picture-hook.
WordPress is first and foremost a blog application, so I guess trying to extend it to galleries is always going to be doomed to some sense of failure.
What I might try and do is make Coppermine more WordPress-like and use some SEO and Lightbox plugins (if they exist). I'm basically after full-feature gallery infrastructure rather than hacking WordPress to be a gallery, so having everything automatically set up rather than having to create pages for galleries/albums, plus nested galleries/albums and intermediate copies and thumbnails.
If anyone had any suggestions, they're by all means welcome.