Mountain Biking - Road clipless on MTB?

I know a lot of recreational roadies use MTB clipless pedals and shoes on their road bikes b/c of the cleat design, but I went ahead and bought the traditional road styled clipless pedal and shoe.

My question:
Will using these road items on a MTB during off road riding be dangerous? Mind you that my riding won't be DH or FR, but more some pretty intense XC and trail riding. I just don't want to have to spend another lump sum for mtb stuff.

I guess I shouldv'e gotten MTB stuff from the start, but hopefully the road equip will work just as well :/ ?

Thanks!

Edit: I guess another thing to ask would be what the major difference between mtb/road pedals/shoes are besides weight.

You can't walk in road shoes. Also, tension might be so high that it can get scary trying to pull out.

In general I'd say mountain pedals/shoes are fine for road, but not really the other way around. I'd get some cheapish mountain shoes and shimano SPDs. The latter are relatively inexpensive. You may be able to keep it around 100 bucks for the both if you shop around.

The thought of trying to mountain bike in road pedals scares me.

The tension is higher, hence harder to clip in, and more importantly, clip out.

Moutain bike shoes have treads and cleats. Road shoes are flat. I couldnt imagine trying to walk in a flat bottom road shoe with that monster cleat on the bottom of the shoe.

I can walk in my mountain bike shoes.

Those road pedals will be useless if they get caked up with mud.

If you're riding flat gravel fire road type trails, where you dont have to clip in and out alot, you're should be ok. If you riding technical trails, you need MTB shoes and pedals. You clip out in the middle of a climb, I dare you to try an walk up that trail with road shoes on. The shoes wont have anything to grab into because they are flat.

Mountain bike pedals are double sided. Look style road peals arent. Not that its a huge dealbreaker, but I actually use mountain bike pedals on my triathlon bike because I can get into the pedals very easy and I can run through the transition areas in my mountain bike shoes. Same would hold true on the trails. Its going to be a real pain in the arse. Heck some of the newer pedal systems, like the Eggbeaters, are four sided!!!!