Story Time
I've seen the Rod of Wonder used exactly once in a 3.5 campaign, during character creation.
The campaign started at level 30, which should tell you all you need to know about the resources available to the PCs. The character in question had some ability to manipulate random effects (I forget the exact ability, but it basically allowed them to roll twice on the Rod of Wonder table and choose which effect happened).
The 3.5 version of the Rod has a slightly different table. Critically, Pathfinder's entry for 66-69 is "Reduce wielder two size categories (no save) for 1 day." where the 3.5 version is "Reduce wielder to 1/12 height (no save).". The 3.5 version is unclear as to whether the reduction is permanent (it references a spell, but then explicitly acts differently from the spell), so the GM ruled that the reduction was permanent; for some reason, the GM also ruled that the shrunk creature's speed was unaffected (maybe we had an old book?).
Anyway: the player in question was aiming for the "shrink" option, and got it (twice!) before anything truly bad was forced upon him. His mini was actual size.
As a caster of some sort, that was fantastic for him: he got a massive size bonus to ranged attack rolls and AC (not to mention stealth) with very few drawbacks (he did have an increased risk of being grappled, but freedom of movement isn't that hard to come by).
He then kept the rod in his inventory, but it was never seen or used again.
Theory-crafting (lite)
As a player, I cannot fathom using the Rod in a normal game outside of extreme circumstances (as John Dallman's answer noted: it's simply too inconsistent and potentially-harmful.
As a GM, I have a hard time seeing players using the Rod for much the same reason. ... although, I do know a couple of people who enjoy pulling cards from the Deck of Many Things, so YMMV (on the other hand, the Deck is rarely, IME, used in combat, which does change the math a little).
Regarding:
I doubt I'd use it myself as-written - many of the "good" effects are offensive spells with fairly low save DCs for the level when PCs can afford it. Even a good effect isn't likely to be action-economical.
The vast majority of magic items with fixed DCs offer "fairly low save DCs for the level when PCs can afford" them (and, that's often a generous description). Staves are about the only magic item worth using offensively with save-based offensive spells, once the PCs can reasonably buy them. So, that part of the Rod isn't surprising. That's not why I'd skip it, though; I'd skip it because of the paltry 38% chance of the effect being "probably helpful" in the first place.