I can't speak highly enough of this company - it was truly one of the best trips we have taken (Turkey and Africa - with other tour companies - being the other two).
Four of us went on a 3-week private tour of Vietnam, Cambodia, and Laos all arranged by Kata, the representative who helped us. We had an excellent experience, including the sights, the guides (Rom in Siem Reap and Thuy in Saigon were fantastic), the hotels, and the restaurants (yep, that's the whole shebang!). We loved every other hotel and every meal with two exceptions. The Chateau Restaurant = Restaurant Chateau in Saigon wasn't good and the Moonlight hotel was nice but El Dorado in Hue might have been better - although others seem to love Moonlight).
Kata answered a kajillion questions prior to the trip with patience and reassurance. The itinerary was very flexible; we could add and eliminate activities as we pleased - even when we were there. You won't realize certain things until you're there, so you may want this kind of flexibility. A couple of the guides suggested a few additional activities that were fantastic.
A couple of side notes: Vietnam Airlines is the best of the worst, so if you're flying within the country or to Laos or Cambodia, be prepared for changed flight times. The planes themselves were fine. If you start playing with the itinerary, keep hotel check-out vs. flight/drive times in mind (unless you don't mind sitting around for a while with nothing to do). And do a street food tour with one of the guides - or two! Our street food tour with guide Duan in Hanoi was wonderful.