Interface Data Transformer R11.5.10 Usage & Performance

 My client expects to load monthly TB from legacy system into R11.5.10 and is considering using IDT to change 800,000 balances in legacy 8 segment chart into c.136,000 balances for a 4 segment chart. The box is not confirmed but will be capable of dealing with v. large volumes i.e. AP must create 4 million invoices and payments each night, GL journals with 800,000+ lines will processed every night, expect to have c.1.5m ccid's.  

They are nervous about using IDT, (Informatica is currently being used elsewhere within the organisation).

Can anyone give me reassurance that IDT is robust and performant, and ideally give any comparisons with Informatica? Do we have any client, preferably in UK, who uses IDT on a regular basis?