my experience with QUMI was not good. I couldn't ever get it to focus properly. For that reason I recommend stay away from QUMI, I tried 2 of them with similar (not identical) problems. You can read more about my (and others) problems in QUMI thread if you're interested.
I am going to wait on the new 500 lumen LED's (soon please!!), if they don't come out quickly I will rather just get an acer h5360 or similar.
I should just point out that it's not the brightness AT ALL that makes me want the 500 lumen PJ over QUMI, it's just the focus issue. I think the larger case of the 500 lumens might allow for better lens which hopefully can actually focus an image. brightness of QUMI for me was very good, on screen of slightly over 80"...