This is an old topic, but the problem with this feat is still here...that it's useless. Yes you can get some rare add-ons, but it's not worth the feat point for minor convenience.
It's much better than that.
First, when you disassemble and reassemble something, it's fixed. That means its value, if you're selling it, can jump by potentially a huge amount.
Second, when you disassemble something like, say, a 5mm Hawker with a XM, you can put that on a .44 or a 8.6 Steel Cat and drastically increase the value of that XM. Since the best-selling items have an increasing value multiplier based on the number of attached mods, going from a cheap crappy frame with 1 mod to an expensive frame with 2 mods is a huge deal.
Third, many of the items that you're really interested in don't have a quality value and don't suffer from the 10% hit.
Fourth, there may be a way to mitigate that 10% on the way.
Disassemble is the one feat that can most significantly increase the amount of money in the game. If you're playing on the easier difficulty levels, that doesn't matter to you, but on Hard or DOMINATING, the economy is tweaked so that there's not infinite money any more. Since there are, at a minimum, three big money sinks in the game, it can be quite nice to be able to afford all the optional stuff. So, in effect, Disassemble makes opportunities available that a player otherwise wouldn't have. That's a big impact for a single feat.
The feat most certainly isn't dead; it's merely specialized. That's just fine.