I've got just that. My m-one has been with me for 3-4 years now. I recently aquired a rumour. The m-one now tends to sit and look at me from the console like a sad orphaned puppy dog. (ok, well so I imagine it!) I still like the tc, but it just pales in comparison to the rumour - especially when you listen in context of the whole mix. The rumour has something about it that really works magically in a mix. It's hard to explain. You don't have to pile it on for it to cut through - and it gives a real "high dollar" quality to my mixes. With the tc, it's much harder to find "the edge", where you want an effect to just be present without being obvious. The m-one tends to get lost in the mix at low ratios then all of a sudden it's too much when you creep up the levels. Ok, I'm rambling. Bottom line is that even though I think the m-one is great bang for the buck, I find myself wanting another rumour when I need two different flavors of verbs. Maybe you should consider TWO rumours?
Jon