I just did a test. At 1:05 p.m. CST I sent three emails from my computer:
1) One to my Hotmail account
2) One to my Gmail account
3) And one to my Charter account.
Using my computer I went to the web pages for these accounts and the emails showed up there right away - except for the Charter account. I was unable to check that one because the web interface seems to be down.
At 1:17 p.m. I received on my BlackBerry the message I sent to my Charter account. As of 1:57 p.m. I still have not received the other two test messages.
I called US Cellular customer service. I was told the delays with POP3 accounts is a known issue that RIM is working on. They don't have an ETA on when it will be fixed.