Hey David,
we did some 'spring'-cleaning in (and before) v3.5 and removed all classes that might be... well, 'too much' :) Here is why Tuple2 was removed. Yes, it is a simple class with clear function. However, we believe that if you need class like Tuple2 - a composite of two elements - you should have your own class with much better names that displays what is that class or, what it actually holds. In other words, name 'Tuple' (and method names) talks more about class structure, not about it real type or purpose or content. Imagine you have Tuples of some eg movie data vs music data - these classes should not be the same type, although its structure may be the same. In short, it's too generic for our taste :)
Sorry for all inconveniences - and I hope this make sense :)