Agreed. I wish Mozilla would have left an option to retain the current behavior, even if buried in about:config. Lions native fullscreen mode is so much fail it's almost unbelievable that it ever past any internal testing let alone be released to actual customers.

Only in multiple-monitor setups, and for applications that don't support it well, or at all. It's clearly designed for a single display and trackpad gestures, where it works nicely in most cases.

This doesn't excuse applications (e.g., VMware Fusion, sorta-kinda, and then only in some cases, and apparently now Firefox) that are replacing their existing full-screen support that works better in other situations, alas.

Trouble I see is figuring out what a "universally applicable full-screen mode" should even look like in the possible presence of one or more displays arranged arbitrarily, each with one or more virtual desktops. For instance, on my single 27" 16:9 display, I'd prefer browser and e-reader full screen modes with configurable left and right margins, and PDF readers that force portrait documents ONLY into 2-up, non-"continuous" mode, in all these cases with no chrome whatsoever (even when browsing with tabs), while in VMware, I'd prefer an option to choose either Lion-style or "classic" full screen, as I like both for different applications. But, on the whole, imperfect as it remains, I prefer the Lion set-up to Snow Leopard's in most cases. If I ever have room on my desktop for TWO 27" displays, I might say the opposite (and did, in fact, when I had two smaller screens rather than my current set-up).

And both are better than the Windows 8 preview's "full-screen only for crippled, tablet-style applications" model, because, e.g., I WANT Remote Desktop to stay connected in the background (to be fair, though, Windows 7 and 8 do have better built-in "fullish screen" window management features than any OS X version, but this is very easy to fix in OS X with either AppleScript or third-party tools).

Short of writing my own window manager, Web browser, etc., I'd personally be very, very hard to please all the time. Case in point: should Apple support TWO multi-touch trackpads with independent, configurable gestures? Probably not, but that didn't stop me from finding a workaround (hint: Wacom's latest tablets have gesture support).

Heck, I've seriously considered wiring up a MIDI pedal controller as a hyper key in Emacs, but I certainly don't expect any OS to support this out-of-the-box...