But you can't be forced to switch either, so it's good on something that you plan to keep in and keep boosting it's stats... aka cradilly
Also with leftovers and ingrain, you're getting 1 eighth of your health back every turn... not bad if your pokemon has some way of not ketting killed because it can't escape
Oh man. I hate Cradilies. And I despise Cradily's with leftovers AND ingrain. Those things almost have Blissey potential... Well... Not really. But to my all water teams, they do. Thank goodness for icebeam.
Ingrain is basically like leftovers, though the user cannot switch, and roar and whirlwind will not work on them. It can work to annoy a pokemon and heal a lot, or to stop a baton pass chain be PHazed.