I'm afraid I have to disagree with the consensus here. I also use installous, but not in a bad way. There are so many crap applications being put out (probably the majority) that I would have never purchased had I been able to try them first.
I'll give you an example of my use. There are around 5 different travel apps that i thought "may" meet my needs. They range in price from $4.99 to $9.99. Instead of blowing $25 to $50 to figure out which "ONE" app was right for me, I downloaded all five from using Installous.
I try all five for a few days. Decide which one I want. Delete all five and then go to the app store and purchase the one I decided I like. I see nothing wrong with this.
The problem with not getting to try before you buy is that there are sooo many: 1) crappy apps being put out, 2) so many app reviews being paid for or written by the app developer, 3) so many stories of app developers not responding to your problems or inquiries, 4) apps that cause my phone to crash. The list goes on and on.
I just don't think its fair to use the "herd" mentality to jump on anyone who uses installous. Like most other things in this world, there will always be those who abuse the system. I find it hard to believe, that if everyone used installous the way i do, one person on these boards would complain that installous is a bad thing.
It's like the gun haters. There are great uses for guns. When someone is murdered with a gun, its not the guns fault or the gun that is bad, its the person using it.