IMAP, MS Outlook 2k3, and Blackberry (OH MY!)

Okay, so I've got me a client that now wants his email to show up everywhere using IMAP. He's got an office desktop, a mobile laptop, and the stinkin Blackberry. I haven't been able to test this kind of functionality on my own machinery (aint got MSOutlook 2k3 or a blackberry) but I have access to a machine running MSOutlook 2k7 that seems to not have any fuss with IMAP. The client, however, seems to have so many problems he's now whinging about getting a new mail server. Problems (allegedly):
1..Mail items coming in on BlackBerry and Webmail that are apparently never getting to MSOutlook on either desktop or laptop (the most prolific complaint).
2..Mail items are "inconsistent" with regards to what appears on laptop versus desktop.
3..Client has a "consultant" who sold him the hardware and claims it's a problem with the server (!?).

Obviously problem 3 is something I need to solve myself (..preferably with a baseball bat upside someone's head) but I was wondering if anyone else can relate possible IMAP "gotchyas" they may have encountered using MSOutlook 2k3, or if any actual problems with DH and multiple clients IMAPping to the server are actually pushing the "silk-purse/pig's-ear" envelope.

TIA!