First off, you can forget everything you learned inside the HandyGPS application.  The only icon at the top of the screen that works is the GPS button.  The tape icon does nothing but blink some the screen.  Only the bottom icons of the UbiGo screen work: there is a zoom arc (you can also use the up/down buttons), a drawing tool (make your own maps!), a Point of Interest (POI) marker (a tack), and a search button (binoculars).

A severe limitation of UbiGo is the size of its maps.  Be prepared to dedicate one to two megabytes of memory to UbiGo. if you live in a major metropolitan area.  My map of Harris County, Houston, and a few area towns was over 1.5 MB!  At least you can pick and choose what cities within a county you want to have.  I rarely travel to Pasadena (especially after that speed trap ) so that was one of the towns I removed from Harris County to save some space.

In terms of customization, you cannot adjust the text size, but in Map | Preferences you can setup the greyscale shade and thickness (single or double) for the types of roads.  You can also use the drawing tool to create your own maps.

The Search feature is pretty nice.  You can either search inside a particular map for a particular road, airport, etc. and you can either view the item or mark it as a Goal. UbiGo will show a box at the top right with the distance to the target.

One caveat: you can only search by the beginning of a word (in the screen shown, typing "nut" would not pull up Beechnut St.).  You have to also watch out for roads that have two names.  Decker Rd is also called Spur 55 (I think ) but only Decker is shown.  What is commonly known as Loop 201 is Spur 201 in UbiGo.  Bonus points for those who know where I'm talking about. 

The one thing I like about UbiGo is the Point-Of-Interest (POI) feature.  Tap the tack icon, then anywhere on a map (unfortunately you can't specify the exact coordinates).  Tap the POI icon again to enter the location's information and select an icon for that POI.  I wish POIs and Waypoints were compatible.  It would be nice to use the house and other icons inside the HandyGPS application.

When exiting UbiGo or the HandyGPS application you will get a warning.  That is because the GPS won't function anymore when in other applications.  The satellites last locations are kept, though, so you can reconnect more quickly.