Sweet chili does have some of the bet pad thai (and drunken noodle) in the area. And be sure you are in the Arlington one - the other location isn't as good. Spice and Rice I've been highly unimpressed with (and I think its the same ownership) but I know some friends do love em...

Towards the city hall yum yum hut does decent pad thai. Also the thai place in north cambridge in the little strip by pemberton farms - its still not in the same league as sweet chili but its decent.

If Taipei Tokyo is the one in Arlington I was highly unimpressed with there stuff - it was better than some but...