I use Opera for lots of surfing - for example, I currently have around 60 tabs/sites open in it. I also use Mozilla, because it can have both separate windows and tabs within windows, and can save a group of tabs as a bookmark - very convenient for webcomics, for example. Unfortunately, Opera can do one thing that Mozilla can't - it saves its current state at all times, so if the computer (or Opera) crashes in some way, I start it up and can continue from where I was before. Mozilla ... doesn't. If it isn't bookmarked in some way, it's not particularly easy to find again (I have to hunt through the history for (in this case) the last 55 days to find the sites I actually had open at the time ... ). On the other hand, Opera seems to slow down a lot when too many tabs are open ...
So, of course, tonight there was just enough of a brownout to shut down the computer, and it's taken most of an hour to work out what I was looking at before. I've taken this opportunity to add a bunch of people to my LJ reading list (i.e. "friending") - so if you suddenly notice my name there, that's why - purely self-interest in saving this sort of hassle if there's more power silliness.