Until recently OATS was only supported on 32 bit Windows. I'm still running it on 2003 Server / Windows 7 32 bit (despite 64 bit being supported for the last year or so).
We're load testing a mixture of both java and .NET based applications.
OATS only supports web / http applications. There's no support for 32bits Windows applications like client/server, SAP GUI, Powerbuilder apps or things like that.
If these applications use http as an underlying protocol, we might use OLT, but OFT won't work.
Hope it clarifies.