the app store is a flawed concept. once you have bought that app, you can't get a refund for it. so if that app is lame, you are still jammed. if it's promoted well enough, it won't matter if sirixm produces the worst app in existance because people are still going to purchase and download it. apple can take this app and convert it to more sales for the iphone/pod touch and generate more exposure for sirixm, but unless there is no paid option for these people (ie, purchasing an online subscription for this app only) they aren't going to see much of a financial impact from this app if any.
i think that if there was a 24 hour trial period, apps would both improve in quality and be used more often. i read a report that most app store apps that are newly purchased are used mainly within the first 10 days and usage drops off significantly afterwards. i may get slammed for this, but i use cracked apps to try them before i buy them. and i have bought apps i thought were worth it and use them frequently. its a good idea and one apple should consider using.