Well, let's start with the good news. Firefox's biggest problem over the years has been that it's been a memory hog. The longer you run Firefox, the more memory it eats up. If, like me, you left Firefox on for days and with multiple tabs you could actually lock a computer up just with Firefox alone. That, I'm happy to say, they've made a lot better.
According to Mozilla, Firefox's parent organization, "Firefox 7 now uses much less memory than previous versions: often 20% to 30% less, and sometimes as much as 50% less. This means that Firefox and the websites you use will be snappier, more responsive, and suffer fewer pauses. It also means that Firefox is less likely to crash or abort due to running out of memory." This is especially true if you're running Firefox on Windows.
This is the result of a concerted effort by Firefox's developers called MemShrink. This is a project that aims to reduce Firefox's memory consumption by using more space-efficient data structures and eliminating memory leaks, bad memory caching and memory fragmentation.
So does it work? To find out, I ran some memory use tests using first Firefox 6 and then Firefox 7. For these tests, I used my Gateway DX4710 Windows 7 SP1 test box. This PC is powered by a 2.5-GHz Intel Core 2 Quad processor and has 6GBs of RAM and an Intel GMA (Graphics Media Accelerator) 3100 for graphics. It's hooked to the Internet via a Netgear Gigabit Ethernet switch, which, in turn, is hooked up to a 60Mbps (Megabit per second) cable Internet connection.
I then pointing the Web browsers to my iGoogle (http://www.google.com/ig) page. IGoogle is a dynamically updated landing page. Over a day of otherwise sitting idle on this page I found that Firefox 7 had used 23% less RAM than its Firefox 6 sibling. Hurray! More memory management work needs to be done, but it's still a lot better than it was.
Firefox 7 also has several other significant changes. One that I'd encourage Firefox users to use is Telemetry. This opt-in system anonymous reports on your memory usage, CPU core count, cycle collection times, and startup speed. The laudable idea behind the program is to enable Firefox programmers To control this option, which is off by default, head to Options, Advanced, and look to the Submit Performance Data box at the bottom of the General tab.
A minor change, and one that I'm not too crazy about, is that Firefox now hides the 'http://' prefix in URLs by default. As someone's who always copying and pasting URL addresses, that's annoying. Anyone who writes a blog or copies and pastes Web addresses into social networks will also find it vexing. Some blog and networks can render URLs properly without "http://" as part of the address, but a lot can't.
On the more positive side, Facebook's built-in and encrypted bookmark and password saver, Firefox Sync is working much faster. You'll barely notice it keeping your passwords and bookmarks in sync between your PCs, laptops, and mobile devices.
I've also been pleased to see that Firefox is getting along better with my systems. I run Firefox on Windows 7, XP, several Linux distributions, and Mac OS X Snow Leopard and Lion. Unlike Firefox 6, I haven't seen it hang up yet.
That was all the good news, now for the rest: Firefox's performance continues to lag the best.
On the HTML5 Test, which checks to see how compliant the Web browser is with the HTML5 Web page standard, Firefox 7 once more came in with a score of 313 points out of a possible 450. Chrome 14, however, did even better with a score of 341. IE brought up the rear with 130 points.
So, bottom line, Firefox 7 is the best Firefox I've seen in some time. The Firefox development team has done some great work under the hood. That said, Firefox 7's still no where near fast enough to tempt me away from Chrome as my main Web browser. Sorry guys, better luck next release.