We apologize for this late reply as the wife and I have been rather preoccupied with our day jobs these past weeks.
We must first state that we have never visited the sales gallery of Waterview (well, we did try one time but it was closed). As such, we cannot comment about the quality of the project. But in terms of locations, we do feel that Waterview is less than ideal as it is rather remote.
Back to your question: The wife and I are rather surprised to learn that there are still unreleased units, since the project was launched more than 2 years ago. As for stack 35 that you are asking, you will probably get an unblocked view (of the quarry and beyond) as this stack is outward facing. But given that it faces Tampines Ave 10 and is also rather close to the intersection of Tampines Ave 10 and Ave 1, units in this stack might be rather "noisy".
That's the best that we can offer in terms of opinion. Good luck with your search!