Unsurprisingly, the stats are butt-ugly with Toskala in net and Joey Mac has struggled just as badly on the PK. With these two combined, the Leafs percentage of penalties killed off is a god awful 65.4 %. On the other hand, Gustavsson's 79.2 % would currently rank 19th in the NHL, bringing the Leafs up 11 places from their current ranking of dead last. Now, the Leafs skaters collectively haven't necessarily been great on the PK either (though I do I think they have the personnel who ought to be able to do the job), but competent goaltending would sure go a long way, and the numbers put up by Toskala in particular, as he is at least supposed to be a full-time NHL goalie, are inexcusable no matter what.
Toskala has faced 8 more shots on the PK than Gustavsson, and allowed twice as many goals. MacDonald has faced nearly half as much shots as Gustavsson, and has allowed almost as many goals. That's roughly 13 goals worse than what Gustavsson would've allowed, and about 10 worse than a goalie who stops PK shots at about the average rate. This poor performance in net while short-handed has cost the Leafs several points in the standings so far and hampered them in the race for a playoff spot.
A poster at Pension Plan Puppets asked about how much of an affect the Leafs poor start to the season had on Toskala's numbers. Here's a look at the month-by-month breakdown:
October: 8 PPGA, 20 TSH = 60.0 PK %
November: 3 PPGA, 15 TSH = 80.0 PK %
December: 9 PPGA, 21 TSH = 57.1 PK %
As you can see, Toskala has struggled just as badly on the PK in December as he did at the start of the season, after making progress in November.