Not sure why only three episodes are listed, when other sources online say there were four in this collection.
Alchemists Vs. Homunculi:
This one was just plain awesome. Set towards the end of the show, you are just starting your path towards becoming a State Alchemist. Bradley speaks directly to you, assigning you to Roy Mustang's care. Ed and Al happen to get themselves into trouble right then, so you go off to the rescue!
The animation quality was that of a normal episode, and the fighting was subreb. The "interactive" bits were quite awesome, and I had a big grin on my face after it was over.
Al (in his suit) goes off looking for Edward, where he arrives at the studio who created FMA. He's animated (quite badly, I thought), but the enviroment and other people are all real, hence the "liveaction". I'm not even sure of the purpose behind it. I thought that it was rather lame...
Set after the FMA movie, this is just a fun little short with everybody throwing a party as a celebration of being done with the movie. It wasn't bad, but... it wasn't that great either.
This should be counted as the very end of FMA. The ending of the movie was very bittwersweet, but this little short cheers you right up. I won't spoil the ending, but it shows that everything really did turn out alright in the end. A perfect ending to the show.