i recently opened up a
poll asking this very same question. i think everyone wondering whether they should get a paradise fish should read sylvia's post.
i have a paradise fish in with guppies, dwarf platies and a pair of kribensis cichlids. i have had no problems except for the krib attacking the paradise fish while there were fry in the tank (of whom 24 survived and were sold to the LFS).
my tank is also 2 feet deep and four feet long, with both floating and tall plants. there is a huge difference in keeping an agressive, territorial fish in a 10 gallon and a 100 gallon.
yes, if you are going to cram a fish into a territory too small for it and then make it compete with other fish you are going to have problems. i think most of their unfortunate reputation stems from being inappropriately kept. of course all paradise fish are individuals.
this is how i selected my male:
most LFS sell all their paradise fish from a single tank. paradise males are as competetive as bettas, so putting a four in a single tank is a war zone. but it seems that as the number of tankmates increases, combat becomes restricted between the most agressive individuals. what you want to look for are shy fish with complete fins. the males who have the least desire to fight will lurk away from the group; those males who have fought the least will have the least amount of fin damage. don't wory if he's rather pale. paradise fish markings are pretty uniform within the different color morphs, so whatever fish you select should color up nicely if fed some spirulina.
--EDIT--
mine's three inches long, so he's pretty well fully grown. judging by the size of his mouth, there's no way he could swallow anything over an inch. as i mentioned, i just sold off 24 krib fry at about a half-inch in length. they quit swarming about three weeks ago--and i had ZERO losses between those periods. i saw the paradise try once or twice to eat a fry that swam too close, but he was just too slow. i've not seen him swipe at any of the fry since they approached the half-inch mark, even if they swam within just a couple of inches of his mouth. so unless its something small and dumb like guppy fry, i doubt that my paradise could/would catch and eat it.