When you consider Episode 1, Episode 2, CS:S, TF2, Portal, L4D, and all the other projects Valve took part in, I believe it's been a success. We also don't know whether they've had a separate team working on HL3 all this time. Their engine programmers probably don't have as much to do since releasing HL2, so they could have been at work on an HL3 engine all this time.
Oh and dguy is pretty stupid.
Oh and dguy is pretty stupid.