(Spoilers Ahead...)
I really enjoyed that
From the openeing sequence, right through to the train ride at the end, it was a thoroughly entertaining experience. Also, I liked the way that it was a "Campbells Soup" version of HL2, with the intensity condensed into a shorter experience.
I can see what Valve are trying to achieve here; dipping their toes into the episodic content waters, trying to keep fans happy, and bridging the gap between now and HL3 (which is probably a long 4 years away).
The Developer Commentary also sheds a bit of light on some of the decisions they make (it's interesting to note that Dog shaking his head at Alex when she asks him about the calculations wasn't originally their intention

).
So: short, yes, but certainly rewarding; lots of solid shooting action with an NPC who really does watch your back made a nice change from the clumsy resistance fighters in HL2. And it actually felt good retracing my steps through City 17.
Memorable moments for me:
1. Car ride was aces, especially when hanging over the chasm (reminded me of the rides at Universal Studios).
2. Really nice Citadel sections - and the bit with that huge alien sliding under the floor completely freaked me out.
3. The sequence on the train, just after the crash

That scream will stay with me for a while
4. The section where you need to activate the switch and hop across the electrified water - pure HL1
5. Freeman vs. the Strider. Fucking. Ace. On. Toast.
6. The Ending: Valve are, indeed, cunts.
