I've had two new factory struts fail. Original failed my fault, nasty bump in the road at speed. Most recent one sprayed the fluid out the side fitting, the one the electronics hook up to I think, destroyed all the rubber bushings on that side of the car and wrecked a good set of tires. Still I would use nothing but the factory strut, even so far as to hunt down a good used one if money was really tight, as they should last a very long time.
All the rubber boots wrecked, so I had lots of squeaks, most annoying turned out to be very poor Motorcraft sway bar links, they are plastic and the joints can't be lubed. Replaced with MOOG, no more squeak hopefully ever.
Mess with the factory suspension and plan on resale value taking a huge hit. Its something I look for since I "know" the suspension pretty well, is to find a car with a bad or non factory suspension since they go so cheap.