I replaced my chain drive with a screwdrive Genie last year.
Granted it was like 5 freaking degrees that weekend, but it was a pain in the ass in part due to the weather, and in part due to quality of parts.
the screw is attached using 3- 4 foot long peices that are banded togehter by a little (1/4 inch) collar. IMO opinion, these collars are way too small, and are difficult to handle, especially when it is 5 freaking degrees. I assembled the drive as per the instructions only to find that the thing would not operate because there was too much resistance in the hanger and screwdrive assembly. Keep in mind that it took 2 hours of over head work in 5 freaking degrees to find out that I still did not have an automatic door opener. After disassembling and reassembling 3 times (in 5 degree weather) I decided that the gawddamn thing wasn't machined right. Genie sent me replacement parts and thanks to my extensive practice with assembling the original unit I was able to put it together in about 45 minutes. It seemed to work well!
A couple of months went by and my garage door started spontaniously opening and closing! This was really frustrating as at first it was so intermittant I thought it was my kid playing with the control at first. Then I thought that maybe a neighbor was using a ham radio or something... Finally I called support and they asked me to dissassemble, and then reassemble. Then we got into isolating electrical components... turns out to be a bad sender. They said they would send a free replacement part but I would have to pay shipping. I told them there was no way in hell I was paying shipping on anything after spending a collective 15 hours installing and troubleshooting my Genie device. They graciously acquiesced and waved the shipping.
Its been a year now. And for the most part the door opener has worked well since the sender was replaced. It still balks when it gets really cold (I think that the grease becomes too viscous) which makes me think the original drive assembly might have been okay, but too cold. The little keyring controller was really handy for those days when I biked into work until it fell apart one day.
:beer: