Casual Biker, Looking to Get More Serious With It and Need New Bike?

I've been in the market to purchase a new bicycle, but don't really know to much about serious biking. I've been doing research online and talked to my local bike shop. I know I should be looking for a hybrid. I usually bike 30+ miles a day (looking to increase this to about 50 miles a day) on a 12 year old Wal Mart bike. I usually on roads and smooth to mildly rough trails in a hilly area. The bike shop guy recommended a Specialized Crosstrail. I wanted to know if anyone had any opinions on this bike or any other recommendations. I want to try to keep it under $500 if I can. Thanks guys.