I have two of the TNG tunics - a premiere version in red and standard in yellow. The red one is a medium and the yellow one is a large.
Overall, the premiere line is better quality fabric. As mentioned, they do run small, especially in the waist area.
I typically wear a 40 jacket, and the medium fits great in the chest and shoulders. The sleeve length is borderline, but the waist is probably around a 30 or 32.
The large fits much better in the sleeves and waist, but the chest and shoulders are a tad too big.
I'd recommend going a size up and having it tailored.
Sean