...and are less worried about who is going to buy right now... So you implemented a system that makes people less worried about the most important thing to worry about? OP makes many fine arguments about the pros and cons of commissions, but this one little nit trumps them all. There are many reasons for businesses to suffer and eventually die: capitalization, profitability, positioning, etc. but insufficient revenue…
However, there is a point where you've reached a certain critical mass, where your happy customers market for you, where your own marketing and presence sells the company. Like Fog Creek, which is now an established and known company. At this point you will do better at growing your customer base through marketing instead of commission driven sales, where customer service to the existing customers will do the selling for you, and changing the pay structure of your sales people will align them better to this approach. It also allows you to convert your customer base slowly to those you know will remain with you for longer. I think you still need to keep statistics on sales performance, and deal with bad performers and promote good performers, but these should be closer to a bonus structure and work over longer timescales, like the rest of the staff.