Ask HN : What do you think of the pay-as-you-use model

We want to use a pay-as-you-use model for our project monitoring service (under heavy redevelopment for now) and we want to know what you think about it.

In short, you pay a monthly flat-rate for every user of your team (ex : 10$/user). If you have 2 users, it costs you 20$/month, 3 users = 30$/month and so on.

I already wrote about it here : http://bit.ly/payauu