The thing I dislike about them is I'm kind of getting into a purist phase. These things are rarely tested or balanced. And sometimes their visuals aren't up to quality.
Like the Weathered 10mm, which is the only gun you can expect to have early on that's very effective against small radscorpions. It's better than every weapon you'll find until you probably hit Vegas. And the armor is better than you'll find until on the way to Novac. But the weapon doesn't handle weapon mods properly (it's probably not supposed to handle them at all) and causes visual bugs.
Or the special merchant in Neverwinter Nights 2 that offered, among other high end equipment at a discount, a permanent haste item.
Mass Effect 2 stuff from Steam wasn't bad, I guess. I never used any of it, except the Inferno armor for one level.
I like how Red Dead Redemption did it. It was slightly overpowered, I'll grant, but it still required conditions to unlock, same as the rest. Helps that it was just so cool looking.