There are small differences, mostly in the casing quality. But even the most recent Ms -- fresh from Unicomp -- are of much higher quality than the keyboards used by 99% of computer users. Any M in good condition will be a huge step up for someone looking for an upgrade from rubber dome keyboards (with the exception of the somewhat uncommon rubber dome Ms, of course!).
Agreed.
Any Model M, new or used, in decent condition would be a huge step up for anyone used to typing on a cheap rubber dome keyboard and differences in quality among the Model Ms wouldn't be noticed by the unsophisticated user.
However, unlike many of you geekhackers, I believe the cumulative impact of cost reduction measures by IBM and later Lexmark reduced the overall Model M build quality which generally had a negative impact on the typing experience versus the earlier production models. Granted, these changes were subtle and occurred over a period of years.
Compare the typing experience of an almost 24 year old 1390120 vs. a 1999 NIB 42H1292. The build quality of the 1390120 is superior in every way to the 42H1292 and therefore provides a better typing experience...after 24 years of use.
This phenomenon is fundamental to
any manufacturing operation and is part of product life cycle management. At Price Pfister, we continually sought opportunities to reduce standard costs, while Marketing maintained the perception that the "new and improved" products were equal to or better than their predecessors. Whether it's faucets or keyboards, all that matters is margin and how to continually increase it until the product reaches the end of the road.
OK, enough already, I'll get off the soap box. You'll still have to pry my 42H1292 or Unicomp Space Saver from my cold fingers.