Yes, but it needs security updates and possibly bug fixes. That's the very least you'd expect when purchasing software. I bought Sparrow for the iPhone and Mac directly after they were released and really never used them.

But imagine that you just bought either Sparrow a few days ago, or even worse, made it part of your workflow.

It sucks.

On the other hand, it's always an inherent danger with proprietary software. Open software gets maintained by Debian for like forever ;). I learnt that lesson after the demise of Be Inc.