There have been concerns raised about the Mac App store. Not least of all is the fact that Apple take 30% of the revenue. Also no trials or free upgrades, these have to be via the developers web site.
It's unlikely that companies such as Adobe will be on it. However for small and emerging developers then the 30% that Apple take could be well worth while.
Aperture is on a special offer at the moment but ask for Final Cut Pro and you get nothing, not even a mention.
What is interesting is that you can download individual components from iWork rather than the whole suite, and at good prices too.
Lets see how it progresses over the next few months. Personally without the ability to trial the software then I'm not sure how much I would use it. No point in paying £20 for a piece of software only to find it's not what you really wanted.