"Time and Movement in the Dungeons" contains some interesting deviations from OD&D. In both the LBBs and Holmes, a turn is 10 minutes long. In both games, all armored characters, regardless of whether they wear leather armor or plate, move at the same rate, which is 120 feet per turn (though, to be fair, the LBBs are clearer on this point, because they provide encumbrance values for each armor type).
However, Holmes states that, in combat, "there are ten melee rounds per turn, each round lasting ten seconds." In OD&D, a round is 1 minute long. Holmes has muddied the waters somewhat but making the term "turn" equivocal, sometimes referring to what I guess we can call a "movement turn" and sometimes referring to what we might call a "combat turn," each having a different temporal value. It's a bit frustrating and its presence probably explains why, to this day, I instinctively think of a "round" as being 10 seconds long, which it is not in AD&D (though it is in Moldvay, interestingly). Holmes follows OD&D in assuming that one (move) turn each hour must be spent in rest.
Holmes notes that "DUNGEONS & DRAGONS was originally written for wargamers" in order to explain why distances are frequently written in inches. However, nearly every (all?) examples where distances are noted, such as in spell descriptions or monster movement rates, he uses standard measurements rather than inches, a practice continued in Moldvay but not in AD&D.
Encumbrance rules are present, but they are extremely vague. No weight values are assigned to equipment, so each referee would need to decide for himself the weight of each item. The LBBs include such information, however. Despite this omission, Holmes nevertheless suggests that players keep a careful record of all the equipment their characters are carrying, including where on their person they're keeping it. A sample character, Malchor the Magic-User, is used as an example of how to do this and I find it noteworthy that the text says he wears "boots, loin cloth, robe, girdle, and pointy hat."
I've already covered most of what needs to be said about light in the dungeon here. I'll add only that Holmes explains that dwarves and elves "lose their ability to see 60 feet [in the dark] if there is light within 30 feet of them."
Traps function identically to OD&D (triggering on a 1-2 on 1D6). Doors also follow OD&D, being usually closed and forced open on a roll of 1-2 on 1D6, though Holmes includes no suggestion that "lighter characters" open doors only on a roll of 1. Doors automatically close unless spiked/wedged, but always open for monsters unless specifically prevented from doing so. Holmes does not include rules for spikes slipping free, as OD&D does. Listening at doors follows the LBBs (roll of 1 on 1D6 for humans and 1-2 for demihumans), with undead making no sound.
Surprise is handled identically in both (1-2 on 1D6), although Holmes lessens the possibility that a surprised character may drop whatever he is holding.
Wandering monsters are rarer in Holmes, as the referee only checks for them once every three turns as opposed to once every turn. Again, this is a Holmes-ism that I instinctively follow and have had to work hard to correct in my mind. Holmes also provides a clearer, almost formulaic approach to determining how many wandering monsters are "appropriate" for a given dungeon and party level than is found in OD&D, although he's not really deviating from the LBBs. However, his wandering monsters can appear farther away (20-120 feet) than in OD&D (20-80 feet).
Fascinatingly, Holmes includes an expanded "Hostile/Friendly Reaction Table" for dealing with monsters compared to OD&D. It's still a 2D6 roll but it offers finer grained results than that in Volume 3 of OD&D (and Moldvay's own table is almost wholly identically with that in Holmes). There's, again, a suggestion that the table results can be modified at the referee's discretion, taking into account Charisma, bribes, etc. There are also simple rules for evading pursuit by monsters that are similar to those in the LBBs but somewhat simplified mechanically.