From what I have heard, if you are going to use your computer monitor to view DVDs, it is better to use (if you have a reasonably fast computer) a software DVD decoder. Also, if you are going to use a TV (the video inputs, composite or Svideo inputs), then a hardware DVD decoder is supposed to be better.
I have been using the WinDVD software decoder (v2.2), a SCSI based system (scsi DVD drive), VooDoo 3500tv, a turtle beach Santa Cruz primarily in 2 channel surround sound to an el-cheapo dolby logic surround decoder and it is fine. The 3500TV can output to the tv in 800x600 and 640x480. My tv does the 640x480 just fine but it does not do the 800x600 good enough (vertical pincushion is bad)).
At this price, I ordered a couple of the Hollywood+ decoders. I will then compare the results. Eventually, I will get an AC3 decoder: the Hollywood+, WinDVD and the turtle beach Santa Cruze all support s/pdif output of a AC3 datastream to an external decoder.
Paul