Months, not weeks. You'd have to use the standalone version for 2 years and 4 months before it became more cost effective. And that assumes that a new version doesn't come out in that time.
You'd have to use it continuously for that time. If you use Photoshop less frequently, ownership makes even less sense. For example, I use Photoshop maybe every few months. It would take me a lot of years of $30/mo to get to $578. And I'd be happier with Adobe when I got there, because I'd be on a current version of the software.
I hope they don't mess this up with crappy DRM, like in their standalone CS editions.
No kidding. Adobe is a prime example of a company that doesn't understand DRM. I don't need your application to constantly hog my bandwidth after I already gave you several hundred dollars.
I decided to delay any further spending with Adobe for as long as possible after how sorry their install/DRM process was for legally-licensed CS4.
Looks like it could be a very sensible option then! At least, if you feel like you are going to need all the latest features of the newest version of photoshop and can't just 'make do' with CS5.