Major spoilers (seriously, don't read unless you've seen the episode. Really):
I think the second song is great. The Cadance/Chrysalis duet really made it for me. The others were enjoyable, but I didn't like them quite as much. I think that's because I really love villain songs in stuff like this (Be Prepared is my favourite from the Lion King, for example) and the second song fit in admirably as a villain-esque song; especially the reprise later on after the changelings have entered Canterlot. Also, I do love the Best Pet and Flim Flam brothers song and listen to them quite often, so that could explain why I love This Day Aria, even on its own.
My biggest problem was that the ending just sort of happened. The music during the Shining Armor/Cadance scene where her love brings his power back or whatever was incredible, but the scene itself just felt like it popped out of nowhere... and it was a pretty cliche way to defeat evil villain X (I am glad that the elements were not used, though). But really, I don't even mind it that much. The fight scene was totally epic (lol at Pinkie's Twigun), and I like Queen Chrysalis as a villain because she's just completely evil. Discord had a sort of humorous, chaotic evil while Nightmare Moon was eventually redeemed (as Luna), but Chrysalis is just flat out evil. And she looks cool (cue fanart!).
Also, Team Rocket's blasting off again!