They're horrible, IMO.
Buy into a $1.25 SnG and win, and you get $4.50. To make the same amount from a Matrix SnG, you've got to win all four tables.
What they effectively do is spread the prize pool out a lot further. Rather than having three people walk away having earned between $1.80 and $4.50 (I'm sticking with the lowest buy-in here), you end up with seven or eight people walking away with between 30c and $2. Everyone stays playing longer and goes broke slower, but they still go broke.