Valve's first stab at episodic content is, on it's own indivdual merits better than most stand alone games.
The answer is, well, no. Not yet at least... not until the episodic format is given time to prove itself, or to fall flat on it's face. That doesn't change the fact that Episode is markedly better than most games on the market currently, if only minutely better than Half Life 2.
The gameplay is enhanced by the addition of more of the thinking-on-your-feet puzzle solving scenarios, and by the presence of an AI teammate for the majority of the game. Alyx's ongoing companionship and narrative, along with that of a few old allies, also help to give the universe a more cohesive, human feel. She makes light of whatever is going on in the game world, and adds in a colorful joke now and then for good measure. That said, the (gravity)gunplay is as satisfying and visceral as ever. It sure ain't broke.
The graphics still look lovely, and the HDR lighting is extremely impressive although blaringly unrealistic at times. I should note that on my system the game froze more times than can be called acceptable until I reduced the resolution, at which point it still looked very good, but didn't quite take on the life of it's own apparent at the higher settings.
Ultimately, if your on the fence about this game, then chances are you haven't played the original Half Life 2. If you have, then there is little question your going to have every desire to continue the sage of Mr. Freeman in whatever form Valve deems appropriate. Although Episode One lacks the punch of a full, brand new opus, it's an introduction to the new episodic presentation of the Half Life universe. Only time will tell if this is a good thing or not, but in the present you can extend one of the most compelling games out there by a solid 5 or 6 hours and be treated to yet another cliffhanger ending.