When I click play at the bottom usually it downloads then lets me get into the main menu. For 1.8 it downloads about 95% of the files, then stops when it's downloading the .jar .

I get this error message when it stops trying to download:

Error: Could not find or load main class net.minecraft.client.main.Main
Java HotSpot(TM) Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

I think it's probably a problem with Java 8 but I just wanted to be sure this is reported, because I couldn't find anything similar in my search.