My husband and I went to Khao San Road for dinner, and it was amazing (and he's a hard man to please!). The atmosphere is great - maybe a bit loud with the communal tables but everyone was having a good time. We had the squash fritters to start which were amazing! Basically any vegetable deep fried is good... I digress... I had the Bangkok style pad thai and my husband had the khao soi. We both loved our food!
One annoying thing is that they don't take reservations so we had to wait for 30 minutes for a table (we arrived at about 6:30pm). If you have somewhere to go (like we did that night), it may not be a good dinner option because you might feel rushed. Also, if you have more than 2-4 people in your party, I would not recommend it unless you go first thing the place opens! Otherwise, you're in for a long wait - especially since they won't seat you unless everyone in your party has arrived.
Overall, good experience and I would go there again.