as with rc and most things i do like to tinker with stuff, so upgrade ability of macs are zero. so if you need more space/graphics processing, ram, anything, upgraded you are SOL, they have decent specs for general usage but in specific fields aside from photography/videos they are "OK" but they were primarily designed with those items in mind so they excel in that area.
replacement parts, and repairs are severely constricted because of how apple operates.
there is not very much in the way of operating system modification, which i understand because it makes it more user-friendly and hard for people messing up the OS accidentally.
i guess its not them at fault, but for the Cad design softwares, they are practically unusable, between not being compatible with, and when they are compatible, not being able handle it.
they are good for what they are intended to be used for, but for what i need computers for, they fall short on.