Introducing Exchange Server 2010 effect on excisting 2003 users

We are planning to Introduce an Exchange Server 2010 Sp1 to our Exch 2k3 infrastructure this week-end, we have front-end back-end configuration, BES Server, Iphones and IPads connecting through ActiveSync, SAP Servers connected through SMTP Connectors and Cisco Unity 4.2 Build 4.2(1)  

Outlook is 2003

The Iphone and Ipad devices are connecting to ActiveSync using IP address of the front end server

OWA users connect using the IP address of the front end server

BB users are connected to BES

We know Cisco Unity 4.2 is not compatible with 2010 (right?)

The problem is we can't have any downtime for the eamil (1200 users)

If we are only planning to install the server and not moving anything to it at the moment, do we need to expect any effect on the existing users? Specially users receiving notifications from the SAP Server, and BB users and the IPhone and IPad users.

in another words, does introducing 2010 change anything on the existing exchange 2003 configuration, or it's completely separate and we have nothing to worry about.
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Alan CoxSr. Systems Engineer | Lead Microsoft CIE Qualified FacilitatorCommented:
Introducing.. prepping, installing won't really change anything until mailboxes are moved.

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MaroinAuthor Commented:
Thanks for the help
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