I'll be tempted to try it on the first, but probably second.

I selected not interested because odds are I'll never try it, but a very slim chance dies exist for a second playtrough with it on. For now though, no.

This mode made me extra excited for this game. I'm 10 hours into my first playthrough on hardcore, and it's a lot of fun. Now I actually loot dirty water and food incase I might need it.

is there a no crash/lock mode?

I like to have fun when I play games.  So no.

Of course I will , being a fan of postapocalyptic worlds this is as close as it gets to those portrayed in movies mainly in the flick The Road or the Mad Max series or the Book of Eli

First thing.  It's awesome. 
 
Ammo weight isn't that big of a deal.  You just can't carry tens of thousands of bullets anymore, which is fine. 
 
Water, food, and sleep need to be watched about as much as radiation from FO3.  No micromanaging. 
 
Hardcore mode is extremely well implemented and I am very impressed with how it enriches the experience.

My answer isn't on there, which is eventually. I'll probably want to have seen every faction side before sinking into a mod which requires serious consideration for such things, so probably 4th or 5th, though at that point it's questionable how far I'd get. Guess it depends on much the mode adds to the experience.

Just finished in Hardcore mode.... apparently you can change the difficulty and still get the achievement.  I was playing on normal but the last battle scene (i experienced) was impossible for me with the PC lag issues i was having.  I tried 12 or so times but in the end i just had to give myself the advantage over the lag by switching to Very Easy.... i died a little inside... but then had a miraculous comeback when i got the achievement in Steam.