I didn't even know about it. This looks awesome. Highly recommend: wrap GNU GLOBAL in a web app (scrape its output, stick it in a database). We did that at Matasano (with dumber tools than GLOBAL) and not only was it incredibly useful, but shockingly, shockingly easy.

I'm not sure what you are referring to for the web app. Are you just wanting to skin what it puts as a hypertext file already?[1]

[1] http://www.tamacom.com/tour/kernel/linux/

I didn't know GLOBAL had a web interface, but we generally want search, highlight, bookmarks, and notes, in addition to clickable cross-reference popups. We used ectags and Pygments.

Makes sense, I think. As I said earlier, I am new to GLOBAL entirely. Something I found as I was building up my new emacs setup at work. So far, I've been impressed. Not sure I'll ever care for the web interface, but the ggtags mode has been a dream. And I've really only used find-references and find-definition.

I've been using GLOBAL with a slightly tweaked gtags.el for almost 5 years now. It's definitely served me well.

Do you run into any practical size limitations?

It works well for project like Linux kernel. Jump/listing references happens instantly.