I recently updated my Safari to Safari 4. I'd figure I'd put in my two cents regarding it, past versions, and other browsers.
At times, it's actually been surprisingly slow. While it's mostly with Facebook, it happens sometimes with other sites too, although that just may have to do with my internets connection.
The thing new Safari 4 users will notice right away is the Top Sites page:
True to its name, this page shows the sites you visit most often, as well as a history search bar. This is similar to the new tab screen in Chrome (& Internet Explorer, for that matter): 
The Chrome/IE page (which I will hereafter refer to as the Google new tab page) shows the top nine sites. In Safari 4, however, you can change the icon size of the site previews, and have six, twelve, or twenty-four top sites shown depending on the size of your choice. Safari 4 also allows users to "pin" top sites on the page, which guarantees they are always there, as well as remove sites from the page. The Google tab page simply and indiscriminately chooses the nine sites you visit most often.
Naturally this can prove to be harmful, especially for, say, a conservative in a heavily Democratic household who enjoys regularly checking Mike Huckabee's website (or, more likely, someone who [stupidly] doesn't use an Incognito Window to look at porn). I find, however, that the Google way of doing things is more honest and realistic to the user. They're the sites you visit most often, and the one your browser knows you're going to check. Why pin a site on the new tab page you're never going to look at?
Honestly, I didn't factor in the shiny, fancy-schmancey wrap-around reflectey Safari top sites page when comparing it to the Google one. Yeah, it's good to look at, but it did not really affect my opinions.
I just got Safari 4, so I haven't quite figured out all the new features and stuff yet. Some new things include smart search and address fields, which will offer common sites and address based off of what you're typing in the window, a grammar checker for us grammar Nazis, automatic history deletion for items older than one month, and iTunes-esque cover flow for looking though history & bookmarks (it's much easier to find a site when you know what it looks like). Frankly, though, a lot of these features the average user will never notice, let alone need.
Safari 4 is also downloadable for Windows (which is nice).
In terms of speed, most tests put Chrome as the winner, with Firefox as a common runner-up, so naturally Apple's claim of "World's Fastest Browser" has been seen as sketchy by tech experts & fellow bloggers from the start.
...Also, this may just be me, but whenever I click on a link within a page, in Safari it automatically opens a new window (unlike Chrome and Firefox, which open new tabs), which I don't like. I can't really figure out how to change that. I'll work on it.
