Hi,
there is also a T4Editor created by tangible engineering. It
supports syntax-highlighting of generated code as well - not only T4
code sections. Intelli-Sense is includeded for T4 as well. In addition
it comes with modelling tools you can use to create input data for your
transformations in addition to good old xml and dbs.
The FREE Edition also includes Intelli-Sense for the most important namespaces, so i would try this one.
http://t4editor.tangible-engineering.com