Out of Pod Experience

While not having any myself, I've had a few friends who've bought them from the bigger companies like Apple and Dell.

They've had no problems, mostly because those companies tend to replace parts with brand new ones if there's an issue rather than fault find.

So while some parts may have had some use, or the casing may have the odd scratch, they're generally the same as the ones being sold as new.

I got a refurbished Dell (at a nice discount) and it's worked flawlessly for years. As Buzzmong said, it's going to be almost exactly identical to a brand new one, they just can't sell it as a new laptop anymore. Mine even came with a decent warranty on it, and I suspect other major manufacturers would offer the same. They aren't going to throw away their reputation by selling you junk and refusing to replace it, so buy with confidence as long as it isn't some random guy on ebay.

The only downside is you probably won't have as much flexibility in choosing your exact components compared to a new custom-built one, since you're limited to what they have in stock at the time. I had no problems finding what I wanted, but if you're really picky about something (case color, for example) you might have to wait a while.