Definitely Slanted Door. They serve Charles Phan's modern and personal take on Vietnamese food. Don't know why Le Colonial is still around... If you're trying to save up, try small and family-run Pagolac in Little Saigon area. The area's a bit sketchy but the food is yummy.
A higher-end authentic Chinese I find amazing is R&G Lounge. This is the kind of menu that's typically served in Asia (I grew up in Singapore). Best to go in a bigger group so you can share family style as you can get to try more options like steamed whole fish or chili crab. My husband and I always go there for our Christmas dinner. ;)
Yank Sing is a good standby for dim sum. They have a wide variety and good service. Ton Kiang is another bet although farther away from Union Sq. Other dim sum restaurants may be less expensive but may run the risk of serving you greasy food.
Both La Folie and Gary Danko are excellent. It just boils down to who's menu strikes your fancy. Although I would agree with bbulkow to highly suggest Benu. Its newer and more California. We went there 4 days ago and it was phenomenal.
Good luck and hope you enjoy your trip here.
That is definitely agar-agar. We use it to make jello-type desserts instead of gelatin in Singapore. That's because its seaweed-based not from cow hoofs :) I feel they use agar-agar in seaweed salads as a filler cause its very cheap and the real seaweed itself is expensive. This way its technically "seaweed" although its been processed and formed into strands.
BTW, even though I LOVE seaweed salad, it also has LOADS of sugar. Be forewarned.