Well, 2 Weeks ago I participated in a game-coding-project at Trier. Some students of ‘University of Applied Sciences’ organized the week with the goal to finish a multiplayer 2D Shooter. They (Robert and Tobi) provided a good framework based on Slick2D to start with including a working basic network-framework.
To make a long story short I took the part of creating the GUI as I thought I had some experiences with nifty gui that also is integrated with Slick2d. Even it seems to be a fast thing it took me the whole week(5days) as we had to split up the whole framework into different gamestates and to write some additional protocol-commands to exchange data from client to server and back. Nevertheless I learned lot about nifty and even I had the feeling to kick it from time to time I know it was the right decision to choose it.
It provides lots off posibilities for transitions like ” when the screen starts take the block and move it in after 1second and move it back when leaving, or fade, or shake or or or” I had some problems with the widgets but in this case ME was more the problem than the framework itselfs :D.
To have at least a bit contributed to the game itself I added a new weapon that is quite slow but follows the target until it reaches the enemy. For that I had to include a pathfinder in the TileMap. Not too hard work but still enough for getting stuck in some traps for lots of time 
Tomorrow is a revival-meeting and I’m really look forward to see some guys again.
Also have a look here: