I'm of the opinion that an informed consumer is the best consumer. I personally haven't seen enough of The Witcher to determine whether it's a worthwhile investment or not. I think that we, as consumers, should absolutely wait until at least Day 1 for this kind of stuff.
Pre-ordering a game that is going to sell well isn't about managing stock or ensuring production orders, it's about bragging rights. It encourages other studios to promote pre-orders with segmented content from different retailers. The Witcher 3 has gone from niche PC game to a large cult following featured on stage at E3. Pre-orders do it nothing.
If the game you're interested in is niche, indie, not getting a lot of coverage, already confirmed to have a limited print run, then go for it.
Pre-orders can be positive in certain situations. This is not one of them.