While I have no direct experience with short haul modems from a Cisco console to a terminal server, I have been involved with deploying many thousands of these beasts in almost any other configuration imaginable (synchronous and asynchronous models).
There shouldn't be any problems. I have seen problems when using multiple interface powered data sets on a single device, like 8 data sets on 8 terminal server ports. One shouldn't load things down too much. Also, some of the interface powered devices may not like RS232 interfaces that use minimal signal voltages (+/- 3 volts). I don't know what the Cisco console signal voltages might be (standard says 3 to 25 volts, if I recall correctly, lots of equipment used 12V, newer systems may use 3 or 5 volt). You are much safer using powered data sets, although they are a bit more expensive.
You may have to play with some settings on the data sets to ignore various control signals. I don't know what the Cisco and TS support. Typically you can set these data sets to act on control signals or to ignore them, which is what I'd do depending on how the TS works. As an example the data set may wait for a Request To Send signal to be asserted before it drives the line. If the interface doesn't support RTS, then no data !
I'd suggest the RAD product, mostly because they were cooperative in licensing the original technology for interface powering and isolation from my old company, Develcon. They've been at it for longer than any others on the market today (with the unfortunate demise of Develcon and Gandalf).
