Hi Peter ...
I agree with Jason that the VG248 is a far better product. We are currently running 5 - VG's in our environment and have had very few problems with them(knock on wood!).
We did purchase an ATA 186 to test out in our lab and it seemed like a pretty flakey product. If you have read this forum for any length of time, you will have seen all the threads that talk about ATA and fax related problems. One other thing to consider is the amount of time and effort it would be to roll out 15 ATA's vs 1 VG248. The wiring for the VG is very neat as compared to the mess you would end up with using all the ATA's.
Check out his link:
http://www.cisco.com/en/US/customer/products/hw/gatecont/ps2250/products_configuration_guide_book09186a0080235135.html
Hope this helps! Rob
