Is it possible to completely delete from the ssd?

The nature of the SSD design makes it impossible to really erase in the true sense, also running eraser on an SSD will actually shorten its operational life.
The best option is to use and create a container on the drive.
And even with TrueCrypt, there are some issues with lifespan of SSDs. For now, erasure and SSDs don't mix.

There's some discussion (especially among my Electronic Engineer friends) that a properly implemented TRIM will permanently erase data. But I don't think there's formal evidence for it.

Well, because absence of evidence is not evidence of absence.