I've been mulling over switching out my Ruger 10/22 for a S&W 15-22 practically since I got it, and some recent experiences brought this issue back the the fore and made me start re-thinking it again.
I really want to get a sub-caliber rifle that is more similar to my AR for obvious training purposes.
I got the Ruger because it was cheaper, and at the time I figured I could get by with it, but unfortunately, the more I dig into it the more expensive it's going to get, and I'm starting to feel that I'm going to dump more money into it (especially after looking at the AR-style chassis) than it's worth dumping into a .22 trainer to get it "close" to an AR.
Vs an M&P15, while not perfect, is MUCH closer, and from my price-point of view, a lot cheaper.
However, after doing some basic research (forum is acting wankery again. ), I do have some reservations.
So- on with the questions;

1)How is the reliability of the M&P Vs the Ruger?
This is my biggest concern after ammo.
Has anyone done a serious M4c-style zillion round side by side 'torture' test with these? I've heard a lot of differing things from "every .22 has a mind of it's own" to "the Ruger is better" to "the M&P is better".
I know the M&P had some hiccups when it came out- from what I've read, it seems if I stick with a new manufacture gun and mags, most have been worked out?
But thats still doesn't 100% answer how it stacks up to the 10/22 for reliability.

2) How are the (S&W) mags as far as durability and reliability?
I hear they're proprietary mags?
Are there any other brands that will work?
If I toss one (S&W) on the ground, smack it, step on it, or have some other sort of oft-encountered unfortunate mag-related experience, are they going to hold together, or am I going to be pissing away 17 bucks every time I sneeze to hard at them?
This is one thing I have not seen covered very well in the reviews I've read (reviews, my ass...)
I also hear there is some mythical specific way one has to load the S&W mags, but I have not seen it covered anywhere...

3) Ammo types-
Right now I can run all the bulk Federal, Rem GB, and even some awful Winchester crap through my Ruger, with no performance upgrades with 95% reliability- only hiccups I've gotten is if I wait to long to clean it, or get the usual dud.
It seems the M&P is a little picky with ammo, although it also seems this depends on who you talk to- some people insist you MUST only run high performance ammo for it to function, and at the same time, I've seen quite a few people in the 15-22 picture/general info thread here that I skimmed through say that it runs fine with the bulk Federal you can find in any wallyworld. Even a few folks that got it to work with the "dreaded Golden Bullet" stuff (although I agree it is super dirty).
If I can run it with the Federal bulk, I'll be perfectly happy, but if I have to shoot exclusively higher performance CCI or Fed. Match stuff, I am going to be seriously screwed- there's not much of that around here in my "local" stores and I am NOT paying shipping for .22 ammo online (unless it's practically free).

I've seen the minor issues such as light weight (so I'll just duct tape a brick to it...), lack of sling mounts, or loss of accuracy using a tight sling (I do occasionally shoot with a sling). I'll just have to address those as I come to them, based on how the more important issues listed here pan out.
On the flip side, it seems if I get a good one, I can kill two birds with one stone and run it in either a 'run 'n gun' configuration, or scope it up and get acceptable accuracy.

Which brings us to the meat of the issue;
4) Would you consider it a good idea to switch out (and by that I mean sell- I'm to damn poor to afford both right now) your 10/22 for an M&P?