I find that the quality of the ammo is the more important factor. I have an AR-7 that I've had for over a decade, and probably put a few bricks through it. I've never had a feed or ejection problem with mine; the exception being that when I was shooting CB caps there wasn't enough energy to cycyle the action, but usually I held my thumb over the bolt to keep the action closed anyways (making it a very, very quiet little shooter, quieter than a pellet gun, but more powerful).

My only problem is that it shoots low, and the sights are adjusted to the max. I'm not worried, though, as I know where the rounds are going and can call my shots within reason.

Most of my problems with 22 lr firearms stem from using low quality cheap ammo, just like with all my other guns. In this case, I tend to avoid shooting lead bullets with a wax coating, which is about as cheap as it comes. Shooting such ammo will gunk up the chamber of my semi-automatics in short order, usually causing a feed failure or preventing the bolt from closing completely, thus causing a misfire. Roughly 80% of the failures I've experienced with 22 lr are due to this or similar from cheap ammo fouling the gun quickly. Even my Ruger 10/22 won't tolerate it. Anymore, the only gun I shoot dirty 22 lr ammo out of is my Ruger Single Six revolver, because everything about it is so manual that it doesn't care really how dirty it gets.

Other problems come from leaving too much lubricant behind in the action with typically similar results. One old 22 lr semi-auto rifle I owned was a Coohey Arms. It was a sweet shooter, but I bought it used, and the firing pin had been peened down from dry firing before I got it to the point that it wouldn't reliably detonate the primer charge, which explains why I got it for cheap. I ended up trading that gun off for a slick little plastic daisy bolt action 22 lr carbine that I used to help train my daughters with. For being a mostly plastic gun, it wasn't a bad shooter in the least. The oldest daughter could snap twigs with it at 50 feet, usually better than I could (I always claim I had too much coffee to drink on those mornings).

As far as the AR-7 goes, I think it is a fine knock-around gun. It is highly transportable, and mine hasn't failed me yet.

As far as 22 ammo goes, it's like any other cartridge, some guns will just prefer a particular type of ammo over another. Other than the fouling issues, I've never had cause to complain about any 22 ammo I ever bought and used. I've probably shot up a couple hundred thousand rounds of various brands, and anymore I favor using plated or jacketed ammo because I don't want to spend so much time cleaning up. The cheap stuff just isn't worth the effort. My top three are CCI Stingers, Remington Yellow Jackets and Remington Vipers.