My answer to this question has consistently been, “Only if you value your time”.

As an example, I just started watching Tekpub’s iPhone Development series. There is currently about 2 hours worth of content (and I believe more is on the way). The cost for the series is listed as $25 on the site.

My guess is the videos will save me about 10 to 20 hours of reading, tinkering, and just generally getting things going. Now assuming I put a value of more than $2.50/hr for my time (and i do :), the purchase¹ would be a no brainer.

I also have a subscription to Peepcode which I have been loving as well.

¹ Disclosure: Rob Conery did comp me a full season pass. However, this came when I was about to personally buy a license so I have no qualms writing this review.