Functional bikes. Not Porn not Anti

Do you find the basket stable enough? The Blackburn rack is nice but the upward pointing 'extensions' make me doubt actually purchasing. Do you think I could bend them?

The rack itself it plenty strong for whatever I'll ever use it for, I've already carried loads with it. But indeed the raised bars of the rack's top shelf (which would be perfect to attach a large tent for instance) isn't the ideal interface for the basket; a flat platform would be more appropriate.
Saying that it's a small-ish / medium basket, which it what I wanted, and for what it can carry, there won't be a problem. I'd say up to 8 beers before the basket starts flexing too much, but then I'd put stuff in the panniers.

If carrying stuff on top is a priority for you, and not so much panniers, a Pelago / AWOL pizza rack is probably better for you.

Like @Sparky said, no chance of bending them (without making a mess at least)