Sounds like the improvements have been subtle for you. I noticed a big change straight away but I was mostly using headphones which could be said to lack in the areas where the Audiophilleo excels. If you're using the T1 exclusively, which is prone to hot treble and has excellent sound-staging capabilities as it is, then maybe the benefits won't be so apparent to you - they might even sound worse to your ears with the acquisition of AP2. Personally, I find that it does improve the T1 but not to the extent that it improved LCD-2 - that was night and day over the Conductor's USB.
It's probably a question of system matching. Don't ask me how a USB interface can have a bright signature but it has been said of the AP2 and my findings tend to confirm that notion.