Superior Threads has a fantastic site with loads of information on threads and tension.
http://www.superiorthreads.com/education/
I still use serger thread for piecing. Mainly because it is there, I have tons of it and it works. I will say though that the thread is thick and makes the seams a little thicker. I probably would be happier if I switched to a thread like superiors masterpiece....lol, but too lazy still!
I would recommend trying different threads, find which one works best for you. It really depends on what you are doing.
Hope this helps!