I ran our other car, a 1.9 TDI Touran with a Valeo SMF for about a month. It was an absolute nightmare, it wouldn't release the gears properly, made a real racket at 2k rpm and generally didn't feel 'right'. It put me off the whole SMF thing to be honest, and I ended up having to fork out for a standard set up again.
I suppose it is all supposition and rumour as to longer term reliability, but then the vibration does have to go somewhere. On the other hand, SMF's are a more tried and tested technology...
For me though running standard on a daily drive an SMF doesn't really offer me anything other than it being lighter I guess. Just drove to work and the clutch held up all the way. I'm wondering if heat is part of the problem, I wonder if it only starts to let go once it's hot. Still going to change it though!
I did have a problem fitting a Valeo kit to mine last year (new engine) but replaced with SACHS DMF before big upgrades.
The standard setup is fine even when remapped so if you can afford to replace, it's better. Maybe you weren't harsh enough to the car this morning lol