I hate to admit it, but I still find myself using MS Office more often than I use OpenOffice. I'm just slow to change to new things and like you, I already know office very well and makes it more difficult to switch.
OpenOffice has some features that Office is lacking (such as ability to export to pdf) but Office has a few things that OpenOffice doesnt (cant think of any offhand, but I'm sure there are some)
The biggest difference is some functions are in different places and some things are worded differently.
And, OpenOffice doesnt come with all the templates that MSOffice has. (but there are a few user contribs that you can download from their site)
What's nice about the OpenOffice 2.0 is they added an Access clone
They already had capability of connecting to databases, but didnt have the Access-like interface in version 1. Slightly off-topic -
As some point I'm going to go full Linux, but like the MSOffice to OpenOffice move, it's just a matter of getting used to it and finding the time for the learning curve. I started to switch last year, but realized my modem is a win-modem (which means it wont work under linux) and since I had dialup back then...
Every few years I consider switching to linux, every time something ends up stopping me (usually unwillingness to spend the $ to get all hardware compatible and reluctance to tackle it, even though I know it's not difficult).
First time I started to switch was several years ago (back in early 1993 when commercial use of the internet was still prohibited, when you had to get programs on net from ftp sites, you fetched text documents using gopher, and when www traffic measured only 1/10th of 1 percent of the traffic on the internet). But back then only part of my hardware was compatible, so that was very short-lived.
Interesting bit of trivia - google uses linux on their in-house systems.