I'm wrestling with this same question. The Epson V700/V750 Pro are very well respected. Plustek's customer service is an unknown to me. I need to research Plustek; their support may be fine. Sticking with an Epson or something like the Hewlett Packard G4050 brings me better confidence with warranty and customer service.
I've not had great results rigging up a home brew slide copier like BackdoorHippie has done, but I may mess around with it more. My results are okay, but not of the quality I'd like and I have a truckload to scan.
My budget will provide only for something along the lines of the Epson V600 or HP G4050. The Epson V600 holds 4 Sides per scan, where the HP holds 16. I cannot afford to pay a commercial scanner and I'd fear losing the slides in transit.
Oh, and per LeicaR9's post, be cautious if you find Nikon Coolscan units for sale -- some pre-date USB 2.0 connections and many lack updated drivers for current operating systems.