Since I just started a new game, I'm right back to the 'all the monsters on my friggin' disks are locked' stage. However, I finally picked out a Melon Suezo to go to work, and managed to reaffirm my view that Suezos are a damn good monster. Therefore, I decided to toss a rating out for them. As per usual, add your own thoughts if you got 'em.
Now, Suezos are your basic Skill-Intelligence monster. They're passable in life (especially with a Melon Suezo's +1 from the zuum side), but are pretty defenseless otherwise. Be ready to smack your enemies hard and fast. However, when it comes to Suezos, you can actually do that, since they actually have an intelligence attack right off the bat (spit), unlike most of the critters, who end up starting with two physicals (like katos, pixies, and even the mighty phoenix). They are also extremely skilled in draining their opponents, since all the moves they have, even the basic ones, are withering. This makes them an excellent antagonizer, as well as a strong one-hit wonder, if you get their intelligence up high enough.
On the bad side, Suezos are... well... bad. They're a naturally evil monster, so you'll likely have to spend some time spanking them for cheating. However, their evil techs can make up for this, so you may want to keep them there long enough to get some good evil techs (good evil?) and then turn them toward the light side again. Personally, I just did without the 'evil' techs, but hey, who's counting?
Suezo combos are almost always an advantage over the base suezo, in one way or another. Try Suezo/Pixie or Suezo/Gali, if you're really looking for that massive intelligence boost, or maybe a suezo/golem, if you'd like some extra power and defense (and surprisingly, their skill and int don't take too big a hit, with this combo). Suezo/jell and suezo/monol are also good choices (although the monol side will give you a big hit to your lifespan), since they'll give you defense bonuses, without hurting your intelligence at all.