This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
By now it should be clear that, for the active computer user, access to a PC/AT machine is a 'given'. Along with your radio, TV, and telephone, it has become 'standard equipment'. Interestingly, it has not attracted much experimenter interest nor anything like a fanatic user group following. Today's generic PC/AT IS a good, solid machine and, by far, the best price/performance personal computing value-- besides which, it continues to absorb an overwhelming portion of major software vendor attention. It has not, however, replaced the Apple II. Why? Many reasons; but, to keep it short: you can't and/or won't do "Apple II" stuff on your PC. This especially applies to experimentation and one's willingness to try out enhancement products from a growing list of new 'garage shop' suppliers. Ironically, when a II user moves from II-only to "two"-- i.e. adds a PC-- there is more enthusiasm for enhancements and, after a brief dip, time spent using the older machine actually increases! For whatever reason, the "endless Apple II" does seem to be on the rebound. Two computers really are better than one.