I use all kinds of thread in my Viking...Mettler, Sulky, Hemmingworth, Gutermann, Madeira.
I wouldn't use Maxilock (serger thread) in my Viking for piecing because serger thread is very fine, and not as strong as construction thread.
Many members here on the Quilting Board use Connecting Threads thread very successfully. It is reasonably priced. I haven't used it myself, but many swear by it.
http://www.connectingthreads.com/thr...did=HomeThread:600902