Portal is one of the few more original non-indie games as of late, and at that, it's a core strength. Like Mirror's Edge, it has great concept, but it is more of an experiment, which ultimately succeeded as a viable game formula. That is, it did so with consideration of the core formula, and the core formula only, if you understand me.
It's... short. A bit too short, might I add. The game had the aura of an adventure module or a DLC map pack; instanced, inventive gameplay, but lack of depth coupled with a very linear flow. Portal succeeds in being a proof of concept, but there is much to be desired, particularly the shedding of the tutorial-aura that was throughout the entire game. I suppose one only must wait for Valve's c. 2015 sequel to Portal 2, but this only a digression...
Ultimately, I suggest that you do play it, but if you're looking for a more long-lasting game out of the entire Orange Box, I'd suggest Team Fortress 2. HL2 w/ Episodes has the total playtime value of a blipvert, counting replay value, so overall I'd consider TF2 to be the best overall value.