Netronix, my first one, which was resurrected (replaced) I hope to sell. (unopened box since delivery)
Opus my prrrrrecioussss I will use until it falls apart.
Kindle 3 to travel with because of 3G (bought for 3G specifically as the only reason, to travel in Europe, proved extremely useful but while at home sits in the cupboard and gathers dust)
iPad to roam around MR these days
(also tribal newspapers as I'm an expat)
Also, in the before-Alf days, Opus was for epub, Kindle for mobi/azw to have access to both worlds. I decided to stick to Opus and try to fend off upgraditis (will have back up Opus soon though just in case)
So, basically I use only Opus and iPad every day. Kindle occasionally. All of them I find useful.