20 points from 17 games since he took over - this isn't great, if you average that sort of return out over the whole season, that would have us one place higher than we are now. However, that does miss the context that we had 6 points from 14 games before he got here - the worst run in our 144 year history, so it might be reasonable to expect that it would take a little time to turn that around, as we saw with Eddie Howe at Newcastle.
Allowing for that, if you look at Lampard's last 11 games, we've got 17 points and if you average that sort of points return out across a season we would currently be going into the final day a point ahead of West Ham in 7th place. Basically I think, from the numbers, it's a little soon to be making any sort of meaningful conclusions, but there are some vague reasons to be hopeful.
On less tangible stuff, what I've liked about Lampard is that he's been flexible enough to change his approach - we've seen him change style and system. We've seen him get it totally wrong (eg Spurs away and the first 45 mins last night), but we've seen him make also be willing to adapt his approach.
He's also a pretty likeable guy - he's won over most of the fanbase and that does actually count for something. I wasn't a fan of the choice of him as manager but I'm more hopeful now than I was when he came in.