I agree, somewhere like Thetford they're ok, where it's a safe bet you're not gonna be taking your foot off the pedal.
The other main downside, apart from the inability to walk, is the single sided pedals. The last thing you want at the start of an XC race is worrying about kicking your pedals over to clip in.
just got the shoes and in the box there was a leaflet showing all compatible pedal systems. it included "shimano spd" instructions as well as "shimano spd-l" and "shimano spd-r"
i think i might be able to use my existing spd's with these shoes? in the diagram on the leaflet the spd's look like these:
Those cleats are originally designed for the first generation road SPD pedals, they would probably work on newer MTB pedals, but the pontoons may foul on the pedal body, as they're not as flush as the road pedals were.
Just out of interest, if you're gonna use SPD pedals, why bother with road shoes? Surely that's just complicating things needlessly, they're not going to be massively stiffer than equivalently priced MTB shoes, but walking will be difficult and you restrict where you can ride the bike.
If you want to use a pedal like an SPD-SL I can understand, but if you're sticking with SPDs, I'd far sooner use MTB shoes.
And it's not you linking wrong, the picture and the description don't match.
They will work fine, you just have no platform to walk on, I've known people twist ankles and such, as you're walking on a very uneven surface, but as long as you keep that to a minimum you shouldn't have problems.
It'll be harder to get into/out of the pedals too, as there's no tread to 'guide' the cleat into the pedal. I'd definitely look to get the SPD-SLs as soon as finances allow, they're lovely pedals.