Wirelessly posted (Thumpers 8700c: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8703e/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)
I installed 4.2 on my 8703e and noticed OS slow downs. I would be afraid of 4.3 being even worse. It seems like the OS is too beefy for the processor, if that makes sense. I think it's best to leave the device with the OS designed for it.
I am intrigued, however, with the IT policy comment. Is that true? If so, it may be worth upgrading to the Pearl.