I had it on my phone for about 3 weeks and I experience no lag, force close, etc etc. But keep in mind that my device is far from stock, so experiences may vary. As a browser it is basic it covers all the basic features like bookmarks, clearing information, tabs, history, cut and paste.
For the X10 I think that this is the best browser, in terms of function. Once major plus is that when using the browser you do not need to depend on the hardware keys. All the important are always displayed on the screen, such as the back function. For me this is a big plus, since the hardware keys on the X10 tend to space out and get loose over usage. The default zoom buttons are already replaced, and are now relocated to the sides. You can hold them and drag them to to area that you want to zoom as well, useless but pretty cool. Another plus is the ease of switching between tabs with the dedicated tab button that will always be with you.
When you open the app you are presented to a nice 3D main menu where you can scroll through your bookmarks and history. Also you can easily scroll through your open tabs as well. Everything is touch friendly and I did not experience any significant lag during usage. When compared to the stock Android browser it is a bit slow but nothing significant.
Overall for the X10 this is a good download and a good substitute over the default browser. It looks nice and gets the job done. It is not as advance and option packed as Dolphin Browser HD but its design wins me over. Dolphin Browser HD was too laggy, clunky, and overall a bad experience for me. Out of 5 I would give this a 3.5 or 4. The only annoyances is that the default search is linked with Yahoo.