I'd say it depends heavily on your situation.
Early game it is very high risk. There's a decent chance that vipers/snakes could probably kill you, or you get doomed or whatever. If you don't care about your characters all that much, I guess there's little harm in it, though it is, in my experience, usually a losing proposition by a fair margin to do this. But there's the odd chance you could get lucky. As an aside, on your list of "things you need to drink semi-safely", I'd be tempted to add a waterproof blanket, or at least remember to set aside your gear that can rust or get drenched. Particularly relevant at low levels.
Midgame, I'd say it depends a lot on what intrinsics you already have, and your race:
Losing teleport control is the obvious worst case scenario and most players are aware of this risk (though they may try to sip anyway).
Losing acid resist can be problematic at times. Most players probably don't bother to save an ant corpse from the PC, none of the usual items that give elemental resistance grant it (elem. gauntlets, RoTHK, etc.), and there are few other monsters in the game that give it (basically just ankhegs, unless you find another ant hill or get lucky with a giant slug). There are only a few items that give this resistance natively, and they either occupy fairly desirable slots (rings, gauntlets) or are pretty rare (BDSM). I've had characters who experimented with pools early in the game find themselves taking 500+ damage from ancient black dragons in the endgame. It's not a huge problem, but something to think about.
Losing intrinsic fire resistance can have implications for the Tower, though admittedly finding the right corpse is considerably easier here.
For short-lived races, pool sipping in midgame is somewhat high-risk due to aging. Potions of youth/longevity are really rare, so if you get a bad bout of aging, it's doubtful you'll have the resources to reverse it unless you've already been fairly lucky, or can alchemy some pots of longevity up.
Considering that only really desirable intrinsics that you can get from pools that can't easily be obtained elsewhere are Paralysis Resist and Invis, unless you are desperate for a wish, I think it's probably safer just to ignore pools entirely. Admittedly, both Para and Invis are very nice intrinsics, but I'm not going to gamble a good PC on getting them.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.