In my mind, the problem is that commission is an incentive to do whatever it takes to close the deal -- especially if you're in an uncapped commission with accelerators. For example, if I'm paid 10% on my first $300k in new business, 15% on $300-499, 25% on 500+, I'm doing everything I can to hit $500k, right?
I (the commissioned salesperson) would lie to my mom if I'm at $490 with a $12k deal on the table. I'll lie to you, and I'll tell you things about our product/service that aren't true. You'll do this one project with us, I'll get my gigantic commission check, and then you'll a) never come back b) tell everyone you talk to about us and c) not affect my commission check. I'll also put on my resume that I "exceeded monthly quotas" and smile. Remember, I'm here to get paid. That's why we're in a commission-based role. [edit: Please keep in mind that I'm giving accounts of what I've seen, not necessarily what I've done. I wouldn't lie to my mom. Others would.]
I believe you can mitigate that problem by paying out over a term, or upon certain achievements (deployed, customer gave us a positive rating, etc.). However, what additional problems does that create in your organization? Is it good or bad to have the salespeople managing (micro or otherwise) the delivery ("selling is not delivering")? Does that compensation model get too complicated?
Call me an optimist, but I wish companies would hire people that want to truly evangelize their widgets, put them on a base salary, and then measure performance. Sales isn't rocket science, it just takes someone who is comfortable talking to people...and when you're selling something you believe in, that's really easy to do.