The tops of the keys are spherical, which I have not been able to find in a modern keyboard (with the exception that the 8 home keys on some Kinesis keyboards are spherical -- or at least were when I bought a Kinesis about 7 years ago -- but 8 spherical keys is much less nice than all spherical keys).

Most external PC keyboards have cylindrical key tops these days, and most laptops have followed the lead of Apple and Sony and adopted flat key tops, which IMHO are much worse than cylindrical ones, which in turn for theoretical reasons strike me as slightly worse than the spherical ones that used to be the standard in the 1970s (and 1980s?). I say "for theoretical reasons" because again I have not been able to get my hands on a keyboard with spherical key tops to try.

Good keyboard technique IMHO requires committing the position of the keys to "muscle memory" so that most keystrokes can be done in a single "ballistic" movement. (Some keystrokes will require a "windup" movement similar to the "backstroke" movement of a tennis racket before the "stroke" movement of actually hitting the ball although in an expert typist, these backstrokes will be extremely subtle -- the point being that these backstrokes are an exception to the general rule of only one ballistic movement per key press.) The theoretical reason for preferring spherical key tops to cylindrical and cylindrical to flat is that the curves give the brain more information about the exact position of the hand relative to the keyboard so that the next ballistic movement is more likely to find its target.

Most keyboards with flat keytops, like modern Apple keyboards, have the little pips or nubs on the F and J keys, and I rely extremely heavily on them when I type on such keyboards, to the extent that I use the hand that is not making a stroke to feel for the nub, but I really prefer the enhanced information about hand position I get from a cylindrical keyboard even if it is a cheap $20 Dell external keyboard or one of the (even cheaper) internal laptop keyboards on a Toshiba that is a few years old (the new ones follow the fad started by Sony and Apple for flat key tops).

Professional piano players can lose their careers if they get RSI, and I get the impression that the risk for piano players is greater than it is for programmers, and there was a piano teacher or consultant named Dorothy Taubman who had valuable knowledge about proper technique. Rather than reading about Taubman technique, it is better to go on Youtube and watch tutorials about it, BTW. As of 2008 or so it was possible to see what I mean above about the necessity (or extreme desirability) of backstroke movements this ways (using videos about the piano exercise called "scales").

Since good technique requires committing the keyboard to memory however, non-standard keyboard layouts (or more precisely layouts different from the ones the keyboardist is used to) are very "expensive" in time required to adapt properly to them, and sadly this Symbolics has a lot of keys in nonstandard positions.

Kinesis "ergonomic" keyboards (the $240 ones) BTW are the worst keyboards I have ever used IMHO because the keys are not coplanar and not "double coplanar" like the good ergo keyboards like the Microsoft Naturals were, so the typist has to memorize the elevation and (in the case of the Kinesis) two degrees of freedom worth of angle of each and every key, which I found pretty much impossible. (Yes, the $240 Kinesis keyboards have "mechanical" keys, and yes, they are superior, but get one of the many boards that puts those superior mechanical keys in one or 2 planes so that their postitions are not almost-impossible to memorize.) Modern Microsoft "ergonomic" boards (except the really cheap white "Natural" ones if they still make those) do not have coplanar or "doubly coplanar" (falling into 2 planes) keys either, and consequently they seem like awful keyboards, although unlike the Kinesis, I have never owned one to try it extensively, and unlike the Kinesis, at least the (spherical, solid) angles of the keys do not IIRC point drastically in all manner of directions (but rather it seems to be mostly the elevation (and for some keys, e.g., B and N, the position) of the individual keys that varies and consequently needs to be memorized).