I have one!! they're VERY good for the price i think, i've been using a Sony Sr5e and its not done certain things i wanted to. Partly why i bought a 500d, although i did comprimise, i wanted to be able to control the aperature manually, which you can't do. Although it does let you choose the exposure compensation, you can set it to under/over expose the images by upto 2 stops.
the manual gives a grid as follows
recording quality - 16GB card - file size
1920X1080 ------- 49 mins ---- 330MB/min
1280X720 -------- 1hr 13min -- 222MB/min
640X480 ---------- 1hr 39min --- 165MB/min
19201080 is recorded at 20FPS (be aware of this)
the other two are 30fps.
you need a class 6 sd card mine is 16gb from amazon for £22 inc,p&P
there is one more warning in the book about prolonged use, aparently an indicator shows if the camera is too hot and you have to turn off the camera to let it cool. I've not had this problem yet but i also haven't used the film mode properly yet. Shouldn't be a problem unless you're shooting some sort of time lapse though?
Hope this helps