Quite right, Tiger79. J2ME GUI will only give you the basic components similar to the basic visual components on desktop PC's. Any extras would require you to extend the components yourself. So it depends on what your target market is. Because of J2ME GUI's small footprint and simplicity, it works on a wider range of devices. Also, I tested the performance against LWUIT and it was much faster. So its simplicity gains you performance and compatibility.
But LWUIT and Polish do have many additional features, such as animation and in the case of Polish almost double the number of components.
After reviewing those two, though, we decided to use J2ME GUI for our new project instead, specifically for compatibility and performance. We started out with LWUIT, but after testing it, it didn't work correctly on quite a few phones and had problems on the Nokia S60 series (very slow for some reason - a known issue), so we weren't comfortable releasing it with LWUIT.
Sometimes you need the flashy apps, though, and when you only need to cater for the higher end phones, LWUIT and Polish are both good options.