I rode the Upper Tampa Bay Trail in September 2011. This is one of the most scenic trails I've ever ridden. And it definitely seems longer than 8 miles. There are 5 trailheads here, some self-pay ($2) some free. See more info and photos on my website: http://www.trailviewmount.com
Underpass is open, it's so nice not having to stop to cross Sheldon now!
This makes the trail 100% better. Crossing Sheldon was not only inconvenient but sometimes very dangerous. Even though there's a controllable traffic light there, I've seen drivers blow through the red light on numerous occasions.
Now being able to ride under the road makes this a pleasant and much safer ride.