yeah that is why I figured trying it on my n900 first would be best, as that is just laying around collecting dust anyway. The first thing I try on a smartphone with a fresh OS is if I can make a call and receive a call without any lagging or freezing while I have an office app or browser open. That is usually where a lot of custom roms already fail horribly. That is the essence of smartPHONE but for some reason on xda, people believe that a custom rom with a cool theme and boasting about a tweaked out kernel is enough to impress. well if the phone shits it's pants immediately when used as a phone, that is a sign for utter failure I'd say ^^. Other things I test are the youtube app playing video, video streaming in the browser and video files from my samba shares. If the timing is good and nothing hangs in a weird way, the ram usage must be decent and video drivers are working great usually. If you get strange artifacts when HW decoding or hangs/skipped frames, the ROM is probably crap. Next is battery time. If the droid 4 lasts more than 18hrs everything is fine. If runs significantly shorter with normal use (browsing, texting, email, phone) some kid on XDA fucked up and it's time to debug or throw out that rom.