I have heard mention that adding melanodin malt can mimic the effects of decoction mashing. Any one had any experience with this? How much melanodin would you add to a 5 gal. Bavarian hefe recipe to add a deoction flavor?
The short answer: whatever decoction does/doesn't do, melanoidin malt does something different.
The long answer: If you want a more pronounced malty character, use the melanoidin malt. If you want reduced hot break, increased hop utilization, and increased mash efficiency, use a decoction. If you want all of those things, use melanoidin malt and do a decoction too!
FWIW I decoct all of my beer with over 40% wheat malt, but my wheat malt is exceptionally poorly modified, so I have to use decoction mashes to get a reasonable efficiency. It's been a few years since I've used more modified wheat malt, but I've heard decoction isn't necessary with those.
The REALLY long answer: http://www.homebrewersassociation.org/forum/index.php?topic=12943.msg164416#msg164416