Schiit Mani - any opinions ?

I love it, too.  Very easy to listen to, great soundstage and deep bass (all with MM cart, I didn't use it much with an MC).  Swagman Labs makes an external power supply for it, which will improve it ever further.  However, even without the upgraded ps, it is a remarkably balanced and authentic sounding phono stage. 

I read that it does not appreciate the connection of step-up transformers for mc heads with very low output.

Can anyone confirm this?

I would think that SUTs added to the Mani in MM (lowest gain settings), not MC (highest gain setting), mode would work. In MC that would overload the input.

Why not call Mike Moffat at Schiit and ask?

I got a Mani 11 days ago. A distinctive step up from my economical Behringer phono pre. I've never had any other phono preamp so I can't qualify how good it is to others in and above its price range. I'm also not sure how long to get fully burned in, thinking a month and it should be fully seasoned. 

I do have one question. I keep it on 24/7. The Mani or the wall-wart PS never gets even a little warm. I figured it is best to keep it on so it's always ready. Is it good practice to keep it always powered up? 

I think so; I keep mine on 24/7.