Mugen said:
But is it really capable of replacing a fixed blade for survival?
Any knife is better than not having one, but if the question is would you be better off with a similar sized fixed blade then yes for many reasons, mainly due to stability issues with the lock.
Now as to how much better off it would depend on factors such as your skill level, what exactly you plan on doing, the details of your enviroment and so forth.
In general a larger knife would be better to have in most cases, up to a machete, axe or parang style blade depending on the enviroment. Smaller knives, especially folders are just able to be carried with you everywhere.
It is like the small mini-kit Ritter sells, this isn't really advocated to replace a larger ruck, you just don't always carry the latter.
... as cuttable metals (thin metals able to be cut

) , thick fabric, ect etc. Then, you needed to make a shelter.. Cutting branches and the like. Would the blade hold its own and stay realatively sharp?
Cutting woods, fabric and such won't do anything, light metals is mainly how you do the cutting. Don't twist the blade, try to make the cuts as smooth as possible, if you do so then you should be able to cut light Al with no real concerns but heavier tins and such will cause significant dulling.
This doesn't mean the knife becomes useless, but you will notice a loss in ability for fine cutting. As a general rule of thumb, when in any such situation try to think about what needs to be done and after you get the priorities straightened out, do the tasks which require the greatest sharpness first.
As well you should carry some means of sharpening on you if you are carrying a knife. You can get some really small hones which fit on a keychain. Sooner or later all knives will go blunt.
longbow50 said:
...you won't be wanting to batan or chop with the blade ...
Doug does :
http://www.bladeforums.com/forums/showpost.php?p=3115556&postcount=18
You can't really chop with folders that light, you can cut wood easier than you can chop it, however you can lash them to poles to make small bill hooks :
http://i7.photobucket.com/albums/y269/CliffStamp/Spyderco/Byrd/meadowlark_baton.jpg
That's a Byrd Meadowlark.
-Cliff