i have recently fitted spd clipless pedals to a bike and am using shimano shoes. i have the pedals set to minimum setting and they work fine, there is play that i can feel in them when rotating either foot (but not to the point of unclipping) and i am comfortable with this. but what is the point of adjusting the tension to a higher degree, i mean they are held firm and easy to use, so what advantage would there be?

The tension adjustment changes how easy it is to clip in and clip out. If you turn the limiting screw all the way in, you may need to slam on the pedal with all of your weight to actually get clipped in. I don't think the tension adjustment has anything to do with how much play there is while you are clipped in.

You have to buy the cleats with 0 float

You are less likely to unclip accidentally if you set the tension higher. It might not seem like a risk, but if you don't have perfect pedal stroke (e.g. you have wayward heels when sprinting) then it could matter.

thanks for the replies. much as i thought, i am happy with the feel, ie, some play there. and with clipping in and out, i did feel a bit uncomfortable about sprinting at first, but there is quite a bit of leeway before the things unclip,. so a bit more comfy now.
will see how it goes for a while then maybe try a little adjustment or 2 and see how it feels.
nobody has mentioned how they feel with their settings, ie, high, low or medium tension. i know it's a matter of personal taste, but would be interesting to see opinions.

I thought SPDs were originally intended as mountain bike clips, so there will always be play. the tension adjustment is just how tight the clip holds. In other words how much effort it takes to clip-in and clip-out. Once you're in, you'll still have the same amount of play, and shouldn't change how it feels...

I have SPD's on my cross bike, and works great... I have it on a pretty low/loose setting, and have never had accidental unclipping issues.

I use SPDs on my road bike too, and have it at not too far from the lowest tension setting, making it really easy to clip in/out but not so much to clip in/out unintentionally

I use medium tension on my SPDs (fixed wheel) compared to a higher tension on my SPD-SLs (road bikes proper). I don't unclip unintentionally but I like to feel a more solid click when I engage. Just a personal preference.

Oh, and I also have a bit of play on the SPDs. It's unavoidable, I think. I'm not sure how effective the zero-float cleats would be really, given the small overall design and the lever effect of your foot on that small area. I am willing to be proven wrong though!

I generally run fairly tight on my road bike pedals, but they aren't SPD. All it takes is one or two accidental unclips during an all out sprint, and you will see why increasing the tension can be a good thing. This is especially true if you have the multi-release cleats. That being said, before I switched to Crank Brothers on my mountain bike, I kept those SPD pedals fairly loose because I wasn't doing any major sprinting and liked the idea of being able to unclip in a hurry.

Practice where the tension is enough to get out quickly in a panic situation.
Whats worse than trying to unclip when you really need to and they don't
let you out in time. ouch!