Absolutely. The actual input functions of a keyboard really haven't changed in 30 years (aside from the addition of windows and media keys, really), so it stands to reason that a really well engineered 30 year old keyboard would remain equally as well engineered by todays standards. In fact, if anything, it is superior to modern designs due to the fact that it cuts no corners in quality of parts and quality control in general.
The brand new Unicomp I have has more imperfections than this 25 year old M. That being said, I kind of like the subtle (mechanical) differences in the Unicomp too.
EDIT: Just wanted to add, aside from the structural and mechanical engineering being amazing; the way they have created a concave mounting plate and as such been able to maintain a uniform keycap shape just screams "genius" to me. Modern keyboards emulate this concave sculpturing by changing the height and angle of each keycap, creating a massive flaw in terms of interchangibility among rows. The 1x1 caps on the M can be pulled off and reassembled on any row (to support alternate layouts like Dvorak, Colemak etc). IBM really just nailed it with the M.