The Festool vacs are overpriced somewhat, as are all their products really, but they do work very well. The bags, when you need to change them, are rock solid due to the compaction. The bags also, despite not having the certification, are virtually as good as a HEPA filter. I've done a bit of a test with plaster dust and other fine particles, which left only a tiny trace inside the machine after an hours use. The added bonus of cord and hose management, and the stackability with systainers make them very useful indeed if you have other festool products.
The ability to use auto or manual start and vary the power for different jobs, especially sanding, make it one of the most used bits of equipment i have.
I balked at the price of them, it's fair to say, but it's in almost constant use and hasnt skipped a beat.