I'm not much of a fan of Underground...and the playable demo of NFSU2 on Burnout 3 was horrible.
BTW, ps2.ign.com had a news item about a new playable demo of GT4 that came out today (originally the Japanese release date for those of you who remember or care).
The article updates the track list yet again...but it's still not the complete list:
REAL CIRCUIT
Nurburgring Nordschleife, 20.84km, 300.0m
Laguna Seca Raceway, 2.60km, 55.0m
Tsukuba Circuit, 2.04km, 5.3m
Fuji Speedway 90s, 4.40km, 38.1m
Fuji Speedway 80s, 4.32km, 38.1m
Fuji Speedway 2005F, 4.56km, 37.0m
Fuji Speedway 2005GT, 4.53km, 37.0m
Infineon Raceway (Sports Car Course), 4.06km, 49.8m
Infineon Raceway (Stock Car Course), 3.22km, 49.8m
TwinRing Motegi Road Course, 4,80km, 30.4m
TwinRing Motegi East Short course, 3.42km, 30.4m
TwinRing Motegi West Short Course, 1.49km, 3.1m
TwinRing Motegi Super Speedway, 2.41km, 3.0m
Suzuka Circuit, 5.81km, 40.0m
Suzuka Circuit East Course, 2.24km, 33.6m
Suzuka Circuit West Course, 3.47km, 14.2m
.....and more!? [note: this is exactly what the magazine says].
ORIGINAL COURSE
El Capitan, 4.79km, 63.0m
High Speed Ring, 4.00km, 8.5m
Trial Mountain Circuit, 3.98km, 50.8m
Grand Valley Speedway, 4.94km, 20.5m
Autumn Ring, 2.95km, 30.0m
Autumn Ring Mini, 1.28km, 16.2m
Deep Forest Raceway, 3.60km, 45.2m
Motorsport Land I, 1.34km, 8.3m
Midfield Raceway, 3.56km, 55.5m
Test Course, 10.34km, 1.7m
CITY COURSE
Costa di Amalfi, 4.02km, 138.0m
George V Paris, 2.49km, 7.5m
Opera Paris, 2.88km, 0.0m
Hong Kong, 2.91km, 6.9m
Citta di Aria, 3.40km, 117.3m
New York, 4.17km, 5.2m
Tokyo R246, 5.12km, 23.2m
Cote d' A zur, 3.35km, 44.2m
Las Vegas Drag Strip, 0.40km, 0.0m
Special Stage Route 5, 3.79km, 21.2m
Clubman Stage Route 5, 2.47km, 14.7m
Seattle Circuit, 3.82km, 43.0m
Seoul Central, 2.72km, 3.9m
DIRT & SNOW
Ice Arena, 1.04km, 0.0m
Grand Canyon, 3.54km, 58.4m
Chamonix, 3.22km, 60.0m
Cathedral Rocks Trail I, 3.52km, 35.0m
Cathedral Rocks Trail II, 1.93km, 31.5m
Swiss Alps, 3.31km, 55.8m
Tahiti Maze, 3.60km, 55.3m