Sealskinz socks

I've got two pairs of shoe covers that are absolutely useless in anything more than a light drizzle. I recently got fed up with messing about with shoe covers at the side of the road and having to dry out my shoes everytime it rains (followed by having to wear damp shoes the following morning) and bought some Shimano MW81 waterproof shoes. Since then I've had nice toasty warm dry feet in all weathers. I didn't even realise how cold my feet were with my old shoes until I got these new ones.

Do yourself a favour and invest in some decent shoes made for the weather and stop messing about with overshoes/shoe covers/"waterproof" socks, you won't regret it!

i wear the heavyweight one's but also have a pair of gore-tex cycling boots on, so feet are toasty and dry but i do have a touch of raynaud's hence boots and socks

Even if you wrapped your feet with cling film and tied it at the top, they will still get wet with sweat over time. I think it's best just to go with something that keeps you warm.

I found that they do keep your feet dry.
However, when the sock gets wet it makes your feel FEEL as if they are wet, and still cold from the wetness. They still make your feet feel crap.
Use overshoes and good wool socks. Or gore tex shoes like the Northwave Celsius GTX.

I've been wearing Dexshell waterproof socks (£12 from Aldi of all places!) and they do a decent job of keeping the water out. Though agree with the above, on longer rides or harder rain you will eventually get water in the top.

I also wouldn't wear them without overshoes. If it is raining that much then having soaking wet shoes even over waterproof socks isn't that comfortable, and drying them out when you get back is a right pain.

They are rumoured to work best with SPD sandals as water can not not pool in your shoe.

They're pretty good but 'thermal wise', just as good as a thick pair of hiking socks. Stopping the water running down your legs and into the socks (already mentioned) is important.

They do keep you warm and dry but in keeping you dry, they get wet themselves and due to the nature of their construction they take a long time to dry out. My feet were submerged in calf deep water on Saturday night and although I could feel the coldness of the water my feet were still dry when I got home, apart from natural sweat.

They do not keep you dry unfortunately. Whilst they are 100% waterproof, in heavy rain the water just runs down inside the ankle. I did read of somebody suggesting the cut off sleeve of household rubber gloves to use as a seal, put them over your socks and then put waterproof leggings over the seal? Not tried that yet.
They do keep your feet warmer though without doubt as they get wet they act like wetsuit socks and your feet warm the water up.
Worth having overshoes but they only delay the inevitable. Also keep your feet warmer though so do get some.