3rd Millennium sounds OK judging by the online advertising and promotional material.
However...it does not claim to be fast germinating (like 2nd Millennium). And the most important attribute seems to be SRP (Self Repair Potential).
It is possible that it is a whole lot different--but they used the name because the name worked so well and had such great results in years past.
Hopefully the slower fill-in will be compensated by the rhizomes which help it to creep and fill-in densely--or maybe the rhizomes are just not long enough to make any difference. When the ad says, "Mixes will with Kentucky or Texas bluegrass"...maybe they mean...it looks horrible without mixing with Kentucky bluegrass. Sorry--no personal experience.
When they say "inherent drought, shade, and traffic tolerance of all tall fescues"...it sounds to me like it is below average for tall fescue in those qualities. If it was best or better--they would say so.