I recently switched from Unicolor (which I've heard is identical to Tetenal) blix kits to the Rollei Digibase kit. I'm liking it so much better because I can mix up only as much volume as I need (I don't mean one-shot). If not used to exhaustion, the Unicolor developer would die on me after six weeks, and the same is true of the Digibase developer.
Also, blix is nasty, gassy, odorous stuff. The separate bleach and fix aren't nearly as bad!