I use adblockplus to block ads
and adblock filterset.g updater
customize google to kill google ads.
I use an external program to block ads in all browers, it works better than adblock. Regrettably, it's Windows only, so I tend to use Firefox more when I'm using Linux, depending on which sites I'm browsing.
Checked it out, doesn't look like I'd ever use it, the Firefox download window tends to sit on my second monitor anyway, I have no problems with the Opera download tab either.
fasterfox for enhanced prefetching
I'm generally against prefetching, no idea if there's something similar in Opera, as I wouldn't use it.
flashblock both for speeding web page loads without auto flash playing
Not sure about the use of this, if ads are blocked anyway, any flash content is either blocked already, or necessary for site navigation. In any case, Opera can easily block flash content, or my third party program can also do so, for all browsers.
Don't really see the point of this one for myself, the default Opera/Firefox download managers work fine, and I use a real FTP client for FTP sites.
IE tab for the super rare pages that wont open in firefox or if i want to see if a page normaly has advertisements.
Opening IE itself isn't much of a hassle, and like you said, it's a rare occurance.
NoScript - disables javascript
Java/Javascript can be enabled/disabled easily in Opera, noscript has some a few nice customizable options, which I do through an external program, or which can be done in Opera with a bit of extra work.
Foxmarks - if you use more than one computer often.. automatically keeps bookmarks synced
I have too much customized stuff on my browsers for this to be useful to me, I keep copies of Opera/Firefox on one of my USB drives to use on computers other than my own. Opera has an add-on to keep bookmarks synced too, works even with the phone version of Opera, and bookmarks can be accessed from other browsers.
Firebug - Immensely useful for web designing.
Firebug is nice, I use it somewhat frequently.
BugMeNot. On most sites with a login field (eg, NY Times), right click on the field and select "Bugmenot". It automatically logs you in with one of many accounts for that site, so you don't need to create one.
Opera has a widget which does the same.
Greasemonkey. I've got all kinds of customization scripts for sites. For instance, I can right click and "Save as" any image on Flickr, even if they're supposed to have that disabled. When I visit Apolyton, posts by various users do not show up on my screen at all (not even the "Click here to view this post" for ignored people). Can download videos painlessly from YouTube also. Duggmirror script automatically redirects me to a mirror of popular digg.com linked sites, which frequently go unresponsive after they get lots of "digg.com" hits.
Opera supports user created scripts as well. I've got the Flickr and Youtube features working in all my browsers already.
The thing is you shouldn't look at it as needing to find extensions to replicate the Opera experience, it's looking at extensions to take it to the next level.
But I prefer my customized Opera experience, extensions allow me to replicate my preferred experience.
Most people don't know what they're missing out on. Check out some of the extensions:
I know about most popular extensions, and checked out a few that I hadn't looked at in much detail in the past, due to the lists people posted in this thread.
You should've seen Opera before Firefox's rise in popularity. Gaudy, tacky, bloaty, ad-ware...it's been playing catchup to Firefox ever since.
I bought Opera back when Phoenix was around, I prefered it for general browsing then as well, although neither Opera nor Phoenix were good for the same amount of sites as they are now. Ad-ware's picked up a real bad rep, they would have done better to have no free version at all.
Both browsers have ripped features from each other, fans of either browser will support it as being more original. Opera is forced to conform to IE/Firefox standards more often than the other way around, simply because of its lower popularity. (ie. they ravamped all the shortcuts for tabs a few versions ago to put them in line with all the other browsers)
I don't know what the latest fresh installs are like, but my Opera 9.02 folder is 21.3MB, my Firefox 1.5.0.7 is 27.1MB.
Opera 9.22 fresh install = 5.72 MB (6,008,182 bytes)
Firefox 2.0.0.6 fresh extraction = 20.1 MB (21,099,056 bytes)
IFirefox has this capability, but it is rightfully disabled by default. It only comes into play by default if the browser crashes -- it restores all the tabs you had open. This is an interface faux-pax Opera has by default, IMO.
Probably should be disabled by default, I use the save session option when I have to close the browser, but if I have a large number of pages/tabs open which I want to all reopen in the future.
I haven't used the Firefox one, so I don't know if it has the capability, but I wish Opera would allow sessions to be saved on a per-window basis. I often keep multiple tabs for different things I'm working on sorted into different windows, and if I could save groups of tabs from certain windows into separate sessions to be opened separately, I'd find it quite handy.
Random Firefox gripe of the day: Is there an easy way to change keyboard shortcut keys without installing an extension?