First, you seperate layer 2 traffic between the customers. They must go through your router to see each other. This avoids a whole host of problems like broadcast storms, two customers seeing internal traffic from each other, etc. Second, you can subnet and assign IP addresses more easily. Whether you are giving out private addresses or public ones, you can assign and reassign each independently. If a group or all your customers are on the same layer 2 network, you will have a hard time changing IP's. You don't want to be calling one customer to have them reconfigure their firewall/router and/or DNS setup just because another customer of yours needs a change. Very poor form. Third, you can more easily keep customer traffic separate from management traffic. Fourth, you can later provide transport services for other ISP's on your wireless network. This is useful for the ISP's who think that renting copper from the phone company is a good deal -- let them rent microwave links from you.
Also let me make clear that when I refer to customers on VLAN's, I'm talking about customer to the closet tower where multiple customers are sharing the same sectors or ring (if the sectors all share the same physical interface). From the tower, our customers are all routed.
Just my two cents here. Search around this forum and others to see who has had to make the switch later or not. Whatever you do, make a consistent design. One of my partners is constantly reminding me to engineer myself out of the system and it's good advice. It helps me resist the temptation to create one-off solutions or configurations which are hard to support later.
Thanks. I'm running a lot of Trango and I have SU to SU communication disabled so customer can't talk to each other by default. The only way they can communicat is if I but them on different VLANs so it routed. I guess it depends on the equipment. Most of our customers don't require public IPs so they can all reside in the same subnet without issue. If I need a Pubilc IP, can setup a VLAN for that particular customer. We manage the CPE router so customers don't need to worry about anything.
We are just rolling out some Mikrotik Hotspots so I'm trying to determine the best way to handle these customers. They won't have CPEs but you can disable forwarding between wireless clients so the Hotspot should work similiar to a Trango AP.