I got a MTI when it first came out and used it for quite some time. I voted reliable but problematic. Not really that it wasn't reliable once I understood its idiosynchraties, but its quirks and difficulties led me to replace it.
I did go thru several firmware updates, so enough I think that it was fixed/stable. But it still had things like if I kept it in record pause for too long, it would shut off. But if at the same time I had the external battery connected, it wouldn't really shut off, it would go into charging mode, and it couldn't be woken up properly, so I'd have to remove the external battery to get it up and running again, and then get it back into record mode. (At least that's how I remember it, I could have it bungled up.) At any rate, I'd never want to have the external battery connected until the recording got going and the set was started. And sometimes I'd forget to plug it in right away and would always agonize over whether I should plug in the external battery mid-set or avoid it.
IIRC, I only lost one recording to the MT's quirks (and had a 16bit backup from my iRiver, so nothing was lost). And that was out of many, many successful recordings. Still, I want something that is more reliable (or gives me the impression of being more reliable), so I got rid of it. And went the to the opposite end of the spectrum and got a 722, though I've now settled more in the middle part of the spectrum with an R44 and D50.