Today, Opera Software released a new 5.1 version of Opera Mini. The main feature of this release is that it's been optimized to work well on low end phones with screens less than 200 px wide or under 4 MB of Java Heap memory.
The optimization was accomplished mainly with a new lighter weight user interface that uses text rather than icons for the "Speed Dial" start page and dispenses with some of the icons in menus. The light UI is used only on low resource handsets.
Users of Smartphones, BlackBerrys and high end feature phones will still see the same graphically rich user interface in 5.1 as they did with Opera Mini 5.0. The images above and below demonstrate the main UI differences on a 176 x 200 px screen. The first image of each pair is Opera Mini 5.0, the second is Opera Mini 5.1
Opera says the update is not critical for users of phones that ran Opera Mini 5.0 well, however there are reports on the Opera Mini User Forum that 5.1 fixes some bugs with QWERY devices and improves scrolling speed and smoothness on Symbian 5th edition phones.
If you managed to download Opera Mini 5.1 during the first hour after it was released last night you might have noticed a mysterious "Clear Shared Locations" option in the Privacy Menu. After users started asking about it on the forums, an Opera employee posted "Clear shared locations should not have appeared there (it does nothing in this case), and has been removed in a subsequent silent update." Which makes me suspect that Opera is working to add HTML5 Location Provider support to a future Opera Mini release!
Opera Mini is most popular in the developing world where bandwidth is slow and expensive and phones tend to be basic or older models. Opera Mini 5.0 did not run well or at all on basic phones like most of the popular Nokia S40 models. With 5.1, Opera is bringing 5.0's features including tabbed browsing, copy/paste and a password manager to a large group of it's loyalest supporters.
Related: Opera Mini 5 Tips and Tricks