Opera just recently released the new Opera 10\.10 browser with support for an entirely new technology (Opera Unite), and they are already on their way for 10.50 which bring almost an entirely new Opera experience.
Right after 10.10 release Opera has also made available alpha versions of 10.20 which includes support for running Opera Widgets as standalone applications, without requiring the browse to run.
On my personal system, running the latest version of Chrome 4 dev (4.0.266.0) and a nightly build of Firefox 3.7 (20091221 -- basically two days old) Opera came out first, boasting a 36% faster speed than Chrome 4, and 73% faster than Firefox.
Needless to say these were not even an alpha quality builds, and any comparison is meaningless in the long term, considering that the results could change significantly by the time the final is released. However it is clear, that Opera 10.50 will compare well whenever it comes out.
The new interface rids itself of the menu -- which can be reenabled though -- and puts tabs on top in the fashion of Chrome. It also now features a button on the top left, in the fashion of the Office menu button in Office 2007 which gives you access to the old menu options.
The browser also features a new graphics library called Vega which allows for much faster performance, more complex graphics rendering, and support for transforms and transitions in CSS. Opera 10.50 will also feature the upgraded Presto 2.50 rendering engine which offers much better CSS3 and HTML5 support with rounded corners, box shadows, offline storage, web SQL etc.
Opera 10.50 also finally makes all the notifications non-modal -- like the notifications in Firefox -- ensuring that your browsing experience is unhindered by popups offering to remember your password.
Finally Opera 10.50 has possibly the best implementation of Private browsing of all browsers. You can open not only private windows, but also private tabs which are demarcated by a lock-like icon instead of the websites own icon. This icon disappears if you expand tabs to thumbnails though, making it difficult to differentiate between private and non-private tabs -- but hey, this is just a pre-alpha so this will surely be fixed in the final release.
It is important to note again that the browser is at this point not even alpha quality, and it will crash a LOT. So much infact that despite using Firefox nightlies and Chrome devs, I found Opera 10.50 unusable in its current state, which is sad, since it is a brilliant browser otherwise.
Overall Opera 10.50 seems to be packing quite a punch, and seems to be a much more significant update to the browser than Opera 10 even tried to be.
Download Opera 10.50 pre-alpha from here