They're useful, and I know the possibilities with Alchemy are amazing, but they're for such a short time that I find them better as a source of money. I NEVER use potions in my playthroughs unless I'm about to die from something and I done have time to use my spells.
I imagine that if you play the game on Master or Legendary they'd be a godsend.
I think that mastering the crafting skills breaks the game very often. The alchemy master perk is not so good, but having lvl 100 Alchemy plus alchemist 5/5, the physician and benefactor is already too powerful.
Enchanting...Extra effect is game breaking unless you intentionally put useless enchantments on your stuffs. But why would you do so?
Smithing...Hmm ok, Smithing is fine, it is not game breaking if you do not combine it with the 2 others.
I use 100 Enchanting and Alchemy to enchant a ring and necklace with ~80% Spell Cost Reduction in Destruction, Conjuration, Alteration, and Illusion.
Hours of grinding for two items and I'm completely set for the rest of my gaming experience. I use enchanting for my follower's gear more than my own.
Fortify Restoration potions.
It's a real pain in the ass, to be honest, trying to get the right percentages. You go from 100% to 600% and 2000% in three potions, so I end up mixing different strength Fortify Restoration potions with different items enchanted with Fortify Alchemy.
I start with four, then switch to three, then two as the potions get increasingly potent until I find a potion that works for what I need.