On another performance note that may apply.
I've found my computer to perform more smoothly and better response time with letting MS handle the visual effects. I've turned some off and there was a lag for response time on most everything.

But when I reset it to windows choosing what's best, it, W7, performed better.
Could be in my mind's eye but I'm more pleased with it's performance.

^Perhaps I should have phrased my comment better. By better choices I meant no database at all rather than a different one. I'll agree that, within its intended scope of use, SQLite is probably as good as it gets right now.

But what exactly is it they're storing that actually needs a database? Favorites? Cookies? Browsing history? How big a performance gain would that provide no matter how big a list you had?

Dunno. Seems like they're swatting a fly with a sledgehammer. Unless they wanted to hold user data in a place that would be relatively easy for something on the server-side to query. Hence my original question: What's it really there for?

Yes, awesomebar/places was the reason for going sqlite. Old dat/html something format was worse! Long lists are not fast and manageable because they are not in sqlite format. You can query all day long in library via commands, there is an extension for this I think, but how many do that? Is 1 out of 1000 interested in Places Query Syntax ? Database can do a lot more than what most see. Sqlite might be overkill if you know all "database" features but is it not almost a standard solution for programmers when they need more than "lists"? Many programs use it or that is my impression.

If sqlite is sqlite regardless of where it is used how to implement must mean a lot. Long time ago I read a database expert freaking out about how Firefox handled places. Make one change and it is like whole database must be reindexed/updated. Why I suffered managing 1000s of bookmarks on old 3.0 version. Hd, whole computer was almost freezing for minutes when you did simple copy/paste functions in bookmark sidebar. That was also powered by sqlite.

History/Places change quite a bit in 4 btw Places got Async Expiration

You can just press DEL for the entry you want to ignore/delete. Or use Library tool. But yes they should extend the already awesome bar. Not so sure about search features, there are extensions for this already, but make it more clear how powerful it actually is. Perhaps add a rollover button or 2, giving access to queries/filters (older than 20 days, only show .com for example) Let users tinker with queries (made in library, can already save search queries/results) without making it too complicated. They could start with adding a "how many results to show" in Options. Some might prefer 25 results instead of default 12 or what it is.

At Outertech we've investigated Firefox performance problems several times and in 90% of the cases they were related to SQLite. The number of transactions Firefox is sending to the SQLite handler is simply unbelievable. Even more so if the browser is idle. It starts all kinds of database "optimizations" which cause constant disk activity. This was the reason why we have decided to invest time to create Chrome and Opera Addons for Linkman (which have been released today).

Very nice.  Thanks for continuing to improve the program.