Though the Isle of Dread has appeared throughout the editions, my group did not make our first foray until last week.
Since time was running out I removed the village in the center and pared down the temple quite a bit, reducing it to like, two rooms connected by a hall. After a short bit of exploration they encountered a single kopru, which did not last long against wizard-based ordinance and Deadly Strike. To be fair I did allow people affected by its domination to keep making Wisdom saves, and if Josh did not have Parry the bite and tail combo would have taken him down pretty quickly.
Josh and Kamon both enjoyed the fighter and rogue quite a bit. They praised the maneuver system as a simple-yet-effective way to give them extra options without a lot of bookkeeping. They both had the Parry maneuver, which gave them a good deal of staying power even without a cleric. Despite that Kamon wished that he had “just a bit” more hit points. Personally I think that given the four-day trek the fact that Josh and Melissa could count their respective Hit Dice and daily-spell expenditure on one hand, that characters are pretty durable as is.
Even if they had plowed through all of those encounters in the span of a single day I think they would have been fine. The only thing that really hurt them with the carnivorous ape and kopru, which is understandable because they were 2-3 levels higher (and there were only three characters). The giant crabs and zombies generally had any hits rendered ineffective thanks to Parry, which is likewise understandable because they were 3 levels lower. Despite the low-level the zombies were surprisingly resilient, though I recall Josh doing some really poor damage rolls (and I had a few lucky Constitution saves). We actually liked this, as it conveyed the idea of them being difficult to hack apart besides just giving them a massive lump of hit points.
Kamon chose some decidedly class-neutral maneuvers, so I cannot say that his character felt very rogue-like, as opposed to 4th Edition where rogue exploits had a distinct mechanical feel from the fighter (generally involving lots of movement and damage spiking). I think that by creating a stronger thematic divide (as well as creating other lists for warlords and two-weapon fighters), as well as adding in class features (like weapon and armor stuff for the fighter), that it will help differentiate them.
We did not get many chances, or to be more accurate see many needs, to use wizard spells. Aside from web the only other spell I recall Melissa using was scorching ray, which dealt a reliable 20 fire damage (well, 10 since she was zapping the kopru). Unsurprisingly none of us are a fan of the magic system, even with the tradition addition. Mechanically it does nothing to alleviate the 5-minute workday, especially when by the books you only ever hit 1-2 encounters in a day until you hit a dungeon. Also the whole sometimes at-will, sometimes encounter divide makes even less sense than it did before.
All I can say is, again, please go back and develop the flavor of magic and build mechanics around the explanation, instead of trying to wrap flavor around a mechanic that is not doing what it is intending to do. This goes for both clerics and wizards. How would a wizard explain magic to her apprentice? I think that the sorcerer and warlock were much more evocative and interesting than either the cleric or wizard, and am surprised that they did not recycle their mechanics this time around.