No problems here using good quality .22lr ammo (I've never really tried the real cheap bulk stuff so I'm not sure). I have fired 1K's of .22lr via my 10/22, GSG 1911-22 and even my mouse guns (Beretta Bobcat 21A, PT-22 and a really cheap but reliable little guy, Phoenix HP22). I must admit that my guns always are well-maintained so that may be an important variable for rimfire guns as some others have mentioned.
I will say I have known some who have opted for .25acp BUG instead of .22lr believing it to be more reliable. I like the .25acp round (anything JMB must be great
) but the costs of the ammo is outlandish [but I digress...]).