Although LCDUI provides many ready-made components, some of the items you find in native apps are missing. LWUIT framework provides additional components, and also animations, but it’s still not guaranteed it would offer everything you need.
If you really want to impress your users, you may run into a situation where you need to customize your UI with your own components. Whether you are using Form-based CustomItem or Canvas-based CanvasGraphicsItem, creating customized components is fairly similar. You could even create a generic class that only implements painting the graphics of your component. Regardless of which approach you choose, porting from one to another is a trivial task. The selection between Form and Canvas is dictated by the overall UI you want to build.