I have been using Gokivo a little bit today. Overall I am impressed with what I have seen so far, but I haven't had a chance to use it for any serious navigation yet.
The user interface looks similar to amazegps initially, but user input is more customized for the blackberry. A lot of the menu interface can be controlled using only the trackball. Up and down movements of the trackball move up and down as expected, a right flick of the trackball selects a menu item, and a left flick goes back to a previous menu. I think I have read that this is how is how the Storm's UI works, but it feels strange (at first) on the Bold.
Route choice seems to be better than what I have seen in nav4all and amazegps. For a short local trip that these programs have had problems with, gokivo picked the same route that I would have selected myself. It is difficult to look at the complete route on the map to get a better idea of the selection that gokivo has made. You can show the complete trip, zoom in and zoom out, but scrolling around the map using the trackball is very slow.
One nice feature is that gokivo will tell you the street name during navigation instructions. I don't think I have seen this in any of the free programs. The pronunciation is pretty good for the street names that I have heard it say so far.
Gokivo can also use traffic information to influence its route selection. I haven't had a chance to try this out yet.
Map coverage in the version that I downloaded from app world is limited to the US and Canada. The gokivo website shows coverage of Western Europe as well, but I don't see any support for Europe in the version that I downloaded.
Finally, I don't see any mention in the app that this is just a trial version. There was a brief mention of it being a free trial in the app world description, but I can't find any more information in the app itself or on the gokivo website.