I've been working with SQL Server since version 6.5 - that's a long time! And from my experience most ETL is simple enough that T-SQL works perfectly fine and not only works but works very well - fast, reliable, simple structured programming. I believe anything that can be done in SSIS can be done in T-SQL by someone who knows what they're doing.
Most people who are heavy pro-SSIS, again in my experience, are inexperienced developers who have grown up with graphical tools and don't really know how to program.
