It's possible to learn to remember your dreams. This is also important if you want to have Lucid Dreams. Dream diary is very effective in this process. I used to write my dreams down for a few months and nowadays I can recall my dreams (without the diary) very well, even after heavy drinking and/or smoking session. It sure is fun to remember all that mad stuff thats going on in the night time!
some info about recalling dreams and lucid dreaming:
http://www.lucidity.com/NL11.DreamRecall.html
http://en.wikipedia.org/wiki/Lucid_dream
http://www.wikihow.com/Lucid-Dream
Yup I've found the same thing. I wanted to remember my dreams without having to quit pot, and I found that it's possible by brute force to build recall even when pot is suppressing it. I just couldn't keep it up though and stopped. The thing that helped the most was to write down all my day's events before bed, to practice remembering stuff that I experienced recently. It gave me enough recall to actually recall a dream to write down. Writing down dreams doesn't do a lot of good for recall unless you actually recall a dream in the first place.
On the topic of nightmares, I stopped having them at some point in my life. I'd say I stopped having nightmares when I started smoking pot, but then I also must have stopped dreaming.

But when I go back into dreaming I wasn't having nightmares anymore.
On the topic of crazy dreams after pot, I think my dreams got a whole lot harder to understand after I started messing with my consciousness. Sure, weird stuff happened before, but at least I could english it when I woke up. I suppose pot could have made them whacky, but I bet salvia and such things gave me the garbled up dreams that make no sense whatsoever, the ones where remembering doesn't help me word it one bit. Less comprehensible than fever dreams.
Pot cancels out my insomniatic tendencies and ended several years of being depressed all the time. It also helps me wind down after work. I don't want to throw away all the benefits just to increase the clarity of my dreams, so sadly I'm stuck using effort alone, when effort and no pot together could give me much clearer dreams.
And I've tried melatonin, valerian, st john's wort, and random other herbal stuff. Doesn't work reliably for me. As long as I've had some pot, I sleep no problem. And you couldn't pay me money to take sleeping pills instead of pot. Just seems like a downgrade...