NOTE: a lot of time and optimizations went by since I made the above example (which still uses HOTween v0.8.010). Just so you know: the latest version of HOTween is way faster than what is shown here :)

Basic HOTween Test

The simplest test. On the left you see a trace of some of the HOTween properties that can be read while a tween component (Tweener or Sequence) is running, while on the right there's the trace of two different tweened numeric variables (one uses floats, the other only integers) and two strings, that are animated along the cube.
The tweens are not destroyed at completion because I set autoKillOnComplete=false.

HOTweenController Example

The GUI sliders control the Tweener and the Sequence (loops included) via a simple: myHOTweenComponent.position = GUILayout.HorizontalSlider( myHOTweenComponent.position, 0, myHOTweenComponent.fullDuration );

TipIf I wanted the slider to exclude the loops and control a single run, I would write:

myHOTweenComponent.position = GUILayout.HorizontalSlider( myHOTweenComponent.position, 0, myHOTweenComponent.duration );

Nested Sequences

What the sliders control here is a single sequence (comprised of 2 loops), which is thus easily controlled as any other Tweener/Sequence. The catch is that the sequence itself contains other sequences, and allows for easy setup of complex animations without getting mad calculating each duration.

Changing Parameters While Playing

This demo shows how you can change various parameters (timeScale, loops, loopType and easeType) while playing.

HOTween VS iTween

Here I recreated a speed test similar to the one Jack Doyle (Mr. TweenLite) made for ActionScript's tween engines. I created a "VS" instead than a selection of tween engines, because there are no other tween engines for Unity, as of now (AniMate looked interesting, but I suppose it died, and I couldn't get it to work with Unity 3).

You can get a streamlined UnityPackage (the only difference being that it doesn't use a custom GUISkin) for this test here (code is C# - you might also want to update the HOTween version that is in the package to the latest version, since a lot of stuff happened since I made it, and now HOTween is even faster).

The Emit test type creates tweens that are automatically destroyed at completion, recreating a new cube and applying a random tween each time.
The Loop test type creates an initial burst of random tweens, and then animates them with an infinite loop.
The Yoyo test type is identical to the Loop one, but the loops are of Yoyo (also known as pingPong) type.

Yup, as of now HOTween behaves way faster than iTween, but this doesn't mean that the first is better than the latter. Simply put - as I already wrote - they're two very different engines, for different coding tastes, and they can work quite well together. While HOTween focuses just on tweening, iTween is a Jack of all trades, and automates a lot more stuff than simple tweens.