Basically, you have well over a million acres of park (both a state and a national) in that one area. It's incredible, beautiful, rugged, and you'll remember it for years to come. A lot of hiking, around 200 miles of trails. Within a half day's drive of Big Bend, you have access to many other parks, including a nice spring-fed basin/wetland and large swimming pool (if your of a mind to scuba or snorkel and have appropriate camera gear, you have crystal-clear 30-foot deep water at Balmorhea State Park with a lot of fish), and you have Sahara-like sand dunes in another Texas state park not too far away.
The wildlife can be dangerous, mainly snakes and scorpions were my problem, but as long as you watch where you step or put your hand, and as long as you shake your clothes out and keep your tent sealed, you should be okay. Mountain lions are rare.
The biggest danger is water/hydration. This time of year it's not as bad of a problem, but it can still be one, as well as sunburn.
Take a telescope if you have one, no need to worry about light polution. You will get great sunsets and sunrises.
Big Bend Ranch State Park - 280,000 acres, 32 miles of hiking trails
Big Bend National Park - 800,000+ acres, 150 miles of hiking trails
Hiking Trails at Big BendWhat makes it special (according to them)Some pics that others have taken to give you a feel for it :
http://www.pbase.com/msteffen/west_texas_i...ne&page=allhttp://www.pbase.com/tconelly/bigbend_riogrande&page=allI plan on making a full week-long trip in the fall and can't wait.