I can tell you as a person who is currently looking to buy a 150 I would want the kit installed on the plane I was looking to buy for the very same reasons that Ed Pataky stated (or is that Mr. POOBS to us new people). Every book, every article, and every person you talk to will tell you to buy a plane that has been meticulously maintained and cared for, actually they make you downright paranoid about buying any plane. Yes, the placard complies with the AD but it does add one more question in my mind as to the level of commitment the owner has to maintaining their plane. I would have to ask myself, why wasn’t the kit installed? Haven’t had time yet? Cost? Lazy? Didn’t care? Didn’t find out about the AD because his buddy with the A&P/AI license has been doing “paper annuals” and then the owner found out about the AD just before selling the plane so decided to add the placard because it was cheap?
I agree with Chris. I won't walk away from a plane only because it did not have the kit. Nor would I walk away from a plane with bald tires. I would, however make a mental note to adjust the offer price to allow me to add new tires and the kit - post purchase.
The bigger issue to me, as with Chris, is what message is being communicated? The lack of the kit is a question which needs to be answered. Perhaps the reason is benign, or perhaps its a red flag signaling other issues.
I guess that I'd just want to know.
Roger