I've noticed that my RAM usage in Safari 4 is significantly higher, actually, and especially for apps that use WebKit (like DashboardClient). Overall I'm less happy -- the new tabs are clearly a copy (homage?) to Chrome, but the overloading of title bar / tab is really, really bad for usability. It's confusing to look at a title bar full of tabs and have to think "I want to move this window, what do I click? Can't click the wrong part of the title bar because I might close or move a tab". Chrome does this better by having some space for a title bar above the tabs, and preserving the whole "the address bar is part of the tab" bit. But, while I prefer the old-style tabs, I'm forcing myself to use the new style to convince myself maybe there's something good about it. I'm also fairly convinced Apple will change it by the time Safari 4 ships because of the usability issues.