I am reminded of an answer from another newsgroup.
It went something like this -
Yes, you CAN do it with T-SQL, but just because you CAN does not mean you SHOULD.
Some things that I use DTS (2000 equivalent of SSIS) exclusively for include file and directory manipulation, large(repeated) data transfers where data needs to be cleaned/modified as it is imported/exported, anything involving FTP'ing of files, anything where use of a language that is more conducive to looping would be beneficial, anything with so many steps that to read it in one stored proc would be a nightmare, etc... They are good for anything that needs to interface with a different database platform as well. I prefer the way they interact with front end languages as well, as it can get tedious building an SQL string for a sp with many many parameters.
With the addition of CLR stored procs and functions in SQL 2005, there is more you can do with T-SQL (if you have the option of extending the language in this way). However, when we go to 2005 here at work and I have the option, I think I will actually be using SSIS for more tasks than I currently am because of the move to vb.net or C# from the old vbScript.
So still, without knowing your situation I can't tell you what is best to do. I will say that if you have the opportunity to learn SSIS, then why not? They are fairly easy to learn, very powerful, and a valuable skill to have in the job market.
Hope this helps,
Alex
Ignorance of certain subjects is a great part of wisdom