If you can get a good one used, go for it. Parts are replacable, and it's a very solid machine.
Positive Product Points
Professonal gruppo, heavy brass boiler, very solid chassis. All parts can be replaced, and people actually stock them. You can produce as good a shot on this machine as on any other if you take the time to figure it out and get truly fresh coffee.
Negative Product Points
Compared to the Silvia, the Nancy steamer valve system seems maybe a little less well designed, though mine is old and I'll replace it and see (it weaps). No hot water switch, if you care (I don't).
Others have commented on the funky styling of the Nancy, esp. vs. the Silvia. I have both: the Nancy is an office machine bought used, and the Silvia a home machine bought new. I've had both apart: they are identical in most important respects. The Silvia has a hot water switch, and perhaps a better steam valve. The chassis on the Nancy actually has less flex, and the package may be a little more compact in some dimensions. To tell you the truth, I kinda like the styling. In operational terms, it is not an inferior machine to the Silvia, but I would agree that the Silvia is a better buy new. Either one is excellent for non-commercial (commercial = plumbed, separate boilers) use. Great brass boiler (will not internally disintegrate as some soft aluminum ones I have had did, or fluctuate in temperature as SS are prone to do), and has a great commercial gruppo. Does require a good grinder of Solis Maestro or better quality. You'll appreciate the no-cheater filter basket design and simple steam wand. Both require technique, but give better results. Get fresh coffee (I roast my own, but that's another story--think Makita heat gun and flour sifter) and enjoy better crema than you will get at any shop. I've put in my hrs as a barista (as my daughter does now) and I know of what I speak.
I bought the Silvia from Whole Latte Love, US (I think, it was a long time ago), and the Nancy used from Espressotec, CAN. Both were good experiences. Espressotec is near where I live and they do great parts and service over the counter.