Having just watched the first season and a half of the new one, it's interesting to watch the original. Of course, in some ways it's hard to watch, just as it's hard to watch any show from that era. It's also hard to watch because of how good the new one is. The new one has a really good overall story, and it's executed very well. The original is a little sloppier in its story, and it's executed well enough.
But it's also kind of neat the watch it to see what things were changed in the new one and what things were kept the same. The Cylons were a race of lizards in the original, but they are completely our creation in the new one. They kept the Lords of Kobol, "frak", the playing cards, and the Vipers (the launch sequence is almost identical).
I'm not sure if I'll end up wanting to make it through all 10 discs. Messing around last night, I discovered a feature of the DVD player on my laptop (I watched it on my TV until my DVD player couldn't handle a particularly damaged spot on the DVD; my laptop DVD player is much better at dealing with that kind of stuff). I can watch things from half speed up to double speed with the audio adjusted accordingly. I found that setting it at 1.5 times normal speed let me still catch the dialog. I might try to watch the rest of the series this way, so that it doesn't take up as much of my time but so that I can still stand to watch all of it.