Nikon D3100 vs D5000 vs t2i ( 550 D )

Hey guys,

Looking to make my first feature and looking for a budget dslr. Now originally I was planning on D5000 or
t2i. Now most ppl say t2i wins however I am on a low budget. I have been searching forums and they say D3100 gives t2i a run for its money in terms of video quality. Have any of you had any experience with D3100? I will primaraly use it for shooting video and some photo taking.

Film Riot did a review on D5000 and they said you must always hold the iso button while shooting a movie as once its realeased it goes to automatic iso settings > so in other words, i will always need to have my finger on the iso button to shoot with manual lighting set up.

Is this also the case with D3100?

Which way should I go? D3100 or D5000? D3100 does shoot 1080p at 24 frames which is a plus!