I don't think the in-cockpit sounds are unreasonable. Now, the sound quality in this video isn't great, but it gives an idea. Keep in mind that my camera and I had no hearing protection
(4:00 ish and onwards)
It's a muffled, but still loud, roar with a sort of whooshing sound. So, basically, the sounds aren't far off. Maybe they should be just a little higher-pitch with more piston noise given the engine position.
If you compare to other flight sims, such as the highly praised A2A Spit, the sounds are also similar. (11:00)
Now, the exterior sounds are definitely underwhelming, but I don't think they're final.