Egg beaters are apparently it. You can engage on all four sides and they are light. But you need to service the pedals once a year.
I have some eight year old shimano spds that have never been sevices and work like a dream. The engage when there is brit mud about and works fine after a kick to remove the mud.

Are the beaters worth the the maintainance when you can get the top of the range Shimano's for the same price as the steel egg beaters and maybe never service them?

Depends on how much you like your knees.

Egg beaters have a much greater degree of float so if you've got dodgy knees you'll be able to find a comfortable position for your feet a lot easier than you would with Spuds. The same could be said for ATAC's as well, but Eggbeaters do have the advantage of needing to be rotated at any time if you need to engage in a hurry as you can clip in on any side, not just the two you get with Spuds & ATAC's.

Personally I don't have any problem ewith my Spuds so I'm not bothered by eggbeaters, plus Spuds also have the advantage of the cleats beinmg compatible with a number of other pedals.

Horses for courses I suppose.

i've used shimano, time, crank bros and speedplays takes on the clipless design, the only one which i can honestly say i'd not buy again is the crank brothers, as i just couldnt get on with them.
i'm currently using speedplays.

I've been using Crank Bros Mallets and eggbeaters for the last two years until the other week the cage on me Mallets came away from the axle :-/

Anyhoo to cut a long story short I put on some SPDs for a change and on my first ride out with them they got seriously clogged with mud and I couldn't engage without removeing the crap with a twig.

I also like the fact that if I have an off, my feet always disengage with Crank bros, not so with shimano in my experience.

Personal preference I guess but I like Crank Bros, just a shame about the durability, especially when you consider the price!

Users seem to have change cleat more often with egg beaters than shimano.

I don't like the small contact area of the original egg beaters. If i were to get some i'd get the candy or acid. Where as i'm happy with the spd 515 contact area.