After experiencing some knee pain and my foot slipping off a pedal while going up a steep hill I decided to switch to clipless.
I purchased a pair of Pearl Izumi Quest mtb and a set of shimano M520. Once installed I decided to give them a try. I practiced on the sidewalk outside my house, this might not have been the best Idea because I live on a rather steep hill (about a 4 grade). I tried clipping and unclipping one foot a time. After getting comfortable with it I decided to try while riding. Clipping one foot and kicking off, I was unable to clip my other foot. Trying to clip it and my stupidity, I looked down. I ended up scrapping a wall with my knee and falling. Nothing to bad. I got up and tried again. after a few more fumbles and foot faults I was able to clip both my feet while riding. I rode to a flat and I then started to practice unclipping while moving. I was able to do one foot rather easily. But the other was giving me a problem. This wouldn't be so bad but it was my lead food (the one you start and stand on while stopped). I did a few more foot fumbles before I decided to go back home. Riding uphill (you cant have those great downhill parts with out having those horrible climbs) I had to swerve to avoid a car that decided to cut me off. I tried to unclip and was unable to. When I swerved I hit some road that caused me to dump. One foot unclipped when I fell. I unclipped the other and began to examine my bike. My pedal ripped the cleat out of my shoe. I returned home. took apart the pedal and reinstalled my cleat.

TL;DR Just got clipless. Any tips?

I know a lot of people are against them. But personally like them (ideally) and want to keep them. So please no "just get platform" "toe clips are better" etc

When I first rode clipless, I too had the m520's. After multiple instances of being able to unclip easily (or at all), I lowered the tension of the spring. You should see a hole towards the rear of the pedal, with a + and - on either side. Try turning to the - side, that should loosen the spring and make it easier to disengage. Start off in very tiny increments until you get it right. I'd take it to the flat area you mention and test and adjust there. It doesn't necessarily matter on the foot you don't put down at the stopped position, but you can match the detensioning so that they are equally easy to disenage out of. As you get more comfortable with riding clipless, you can always turn up the tension if you find yourself unclipping unintentionally.

Remember too that the M520s are double-sided, so you need to adjust the tension on each side of each pedal. This fouled me up when I first made the switch.

I have trouble understanding how the pedal ripped the cleat out of your shoe, without wrecking the shoe. I have my cleats set pretty loose, but then I dont pull up hard on the pedals, or do big bunny hops. After a while twisting the foot sideways becomes the natural way to take your foot off the pedals, like up and back was the way to do it with toe clips. Then you dont need to think about unclipping before you stop. If you feel your self falling when you have one foot clipped in, a quick twitch of the handle bars will make you fall to the unclipped side.

I'm pretty sure the cleat wasn't screwed in enough. When it ripped out I think it only ripped out the first 2-3 thread in the shoe. When I felt myself falling I would try to catch myself. But trying to unclip I must have jerked my body in a weird position to throw me off balance. I lowered the tension on the pedals as advised and now I can at least clip in with out a problem most of the time. and the few times I tried to unclip today went a lot better then yesterday.
Another question I had was about platform/clipless pedals. I know when you compromise something you get a ****ty version of the two originals. But I have a beater bike that I want to use in bad weather. Are there any low cost hybrid pedals worth looking at? or just stay away.