You know, that is also exactly the way i feel about Opera, but couldn't just find the right words to decribe it Indeed i feel Opera is clumsy to use compared to Firefox(or maybe it's just that i'm so used to Firefox ? - i don't know...). Yes, i also really like the Adblock extension, and there are also two others that i can't live without : IE Tab + Download Statusbar. The IE Tab extension adds a little icon of the Firefox logo at the right end of the statusbar, and if you then ever visit a page that Firefox cannot show propperly, then you just left-click that little icon, and then the icon then changes to an Internet Explorer icon, and the site refreshes in your current Firefox window/tab, but now it is re-rendered by IE instead of by Firefox's rendering engine, so that now the page looks OK again. Simply a fantastic extension if you ask me. Also it is possible to configure the options so that certain pages always is rendered with IE when entering them like e.g. Microsoft Update(which also is enabled by default). The other extension that i really like is Download Statusbar. It works by whenever you start a download, then instead of that big annoying window opening which you will have to always minimize as to keep surfing the net during the transfer, then instead a little statusbar comes up which shows a little image of the download in progress, and showing the transfer progress in percentage and how long to complete etc. Also it has a wealth of options like e.g. some filetypes shouldn't be showing the statusbar, and instead just download them "silently", so that you don't have to delete them afterwards(deleting items is just a matter of doubleclicking on the statusbar, and then the items + the statusbar goes away). This is really handy when e.g. using something like Foxit Reader as PDF reader instead of Adobe Reader(as it's only about 1.5 MB in size and loads pages instantly), as then the PDF file will just be downloaded and shown, and afterwards when you have viewed the page through and closes it, then you don't need to delete the waiting download item from the statusbar.
Anyway, sorry for blabbing on for so long, i guess i wen't a little overboard here, but it's just that i really like these extensions alot, and that i just thinks that it's just to cool that you are capable to change every little aspect of the browser if there is something that you are unhappy about, which also is why i'm using Mozilla Thunderbird as my preffered mail client of choise