Startup doesn't work for us, we're primarily a carrier and provide our own sip trunks, because we are only a silver reseller we cant get our trunks certified so we cant offer our service on startup. Thats a show stopper for us.
We also have no issues taking care of non start up installs as you guys have built some of the most reliable software i've ever used. The software itself is so rock solid we barely have to provide any kind of debug or maintenance unless there is an update or lightsail notifies us there is some hardware issue with the VM we have allocated to a client (thats happened a few times) and they need to restart the VM or move it, or what ever they do. The problems with smaller clients come from add's moves and changes, things like configuring an IVR, making sure their files are encoded properly, people locking themselves out of the system with password errors, teaching them how to get themselves a new welcome email, how to add a new user and a whole host of other stuff. You've made the software really user friendly but in customer land, the client running a very small business doesn't have time to learn all this stuff and even if they do learn it they rarely remember it next time it pops up as they are busy focusing on their small business and not being their own phone tech.
On top of that though, the rats and mice clients are almost always much hard to deal with, they're either a start up that wants everything free, including all their IT services, their calls, any support you provide and software, or they're just looking to beat you down on everything they possibly can to save every cent they can. We still take them on, we never turn a client away but thats consistently been our experience. You're millage may differ but after 11 years of selling exclusively to business, that's been our experience. The bigger the company, the better they are to deal with all round.