Soldering Lionel tubular track.

If you're joining rails with solder, it's best to use a short piece of wire between them.  Solder will break if it flexes at all, track is pretty stiff.  I've seen layouts soldered like this, and there were a number of broken solder joints between track sections.

I've soldered wires to insulated rails as you have in order to activate crossing gates, signals, etc.  It beats the adjustable contacts any day, in my book.    And as John said, use jumper wires between sections of track.  

I like the jumper wire idea.

I have soldered all of the connections to my tubular track. Just clean the area with a little sand paper before applying the heat. Rosin core solder works best.

I have never found it necessary to solder track together. I Use a track pliers to make sure the sections fit tight and have feeders about every 4-5 feet.