You are right that the decompression seems to be slow work for the N800's processor. Turbo could also sometimes cause delays at the other end, if Opera's proxy servers are busy. These delays counteract the time saving that you get from reducing the size of the download.

The net effect depends on the speed of your connection and the kind of web page you are trying to load. On a fast connection, or browsing lightweight pages, Turbo is likely to be slower than non-Turbo. It's the other way round when you are loading a bloated page via a slow connection.

Here is an example. (Sorry that the web page is not in English. There is an English version at http://www.ferroviedellostato.it/homepage_en.html . My results are for the Italian version.)

Connection: 56k dialup -> Zoom BT modem -> N800.

Web page : http://www.ferroviedellostato.it/

Non-Turbo Opera Mobile took approx. 2 min 30 sec to display the page completely. Tear was about the same. Opera Mobile with Turbo took less than 1 min 20 sec. In all cases, the page had been loaded to the browser on a previous occasion, so any caching effect should apply to all three. Turbo compression reduced the download from nearly 1 MB to about 315 kB.

Another comparison can be made by looking at one of the widgets on the page. The site is about train travel, and the widget in question is for looking up train times and ticket prices. This widget became usable in 19 sec. on Opera Mobile with Turbo, but not until 46 sec. on Tear.