Globalxtreme (
http://www.globalxtreme.net) have just opened in Ubud. They put up a tower and you link to a wireless transmitter. Setup is Rp2m I think and (and I hope I'm not going to jinx this) they have recently gone from being very patchy to very reliable. Maybe because if I goes off I ring and yell!
We have a wifi router in the house and run 2 laptops and 2 pcs off it, often at the same time and it's ok.
Its 512kbs (shared) and we pay Rp1.1m per month flat fee.