Good move Scott! As with Ken and many others, I believe flex track to be one of best advancements in the hobby. It is much faster to lay than sectional, fewer joints to cause trouble, and looks a lot better.
Keep the floating rail to the inside on curves. Be careful of joints in curves. It is almost impossible to avoid having one there so you need to make sure that you don't have a kink at the joint. The kink is a slight misalignment of the rails in the railjoiner. The result of this is a tiny inside edge that will grab wheels, particularly steamer pilot wheels and cause a derail.
There are several methods that everyone swears is better than the other. I will only give you my preferred method.
My way at curves:
A. Connect 1, 3 foot section to straight track and follow your curve. Secure by (I like using track nails).
B. Now you have the inside rail extending beyond the end. Don't cut this off. Instead, take the next piece of track and feed the extended rail into the 2nd piece through the cleats, continue following curve, pushing the new inside rail out its end. Where the two inside rails meet in the 2nd piece, trim the cleats off (usually 1-2 on each side) to allow room to put a jointer in. Do the same on the outer rails that are even with each other. Back the inner rail off a little to get your joiner in place and then push together, same on outside rail.
C. Continue this method until end of curve. Cut the longer rail to be exactly the same as the other and join to straight.
D. Solder each joint. After the initial soldering at joints, place the flat end of a file against the railjoint and reheat while using some pressure on the file. Remove heat an allow to cool. This will align the 2 railends up perfectly and you shouldn't feel any snag on the edges. A file can be used to clean up small snags.
The advantage to this method is the staggered joints will give a very good alignment and provide a mechanically strong connection.
2. Use a yard stick or suitable straight edge to keep straight runs straight.