Both syntaxes "DELETE tablename" and "DELETE FROM tablename" are correct in T-SQL, as far as I'm concerned.
Another problem of using "DELETE" as a substitute of TRUNCATE is that the DELETE will generate a transaction that will fill the log (specially if the table is a big one...).
A limitation of TRUNCATE (as well as DELETE) is that it will generate an error if the table has a relational integrity (as the parent table) with another one (as the child).
If TRUNCATE for any reason cannot be used and you decide using DELETE, then you can also use the DBCC CHECKIDENT to make the proper seed's reset:
DBCC CHECKIDENT ('owner.tablename', RESEED, seed_value)