A common question I am being asked is whether to deploy Exchange 2007 right now (January 2007) in a live production environment. The answer I am giving to everyone is the same - no.
That is not because I do not have faith in the product, or the quality of the product.
I am also not part of the "Wait until Service Pack 1" group who apply that to all of Microsoft's products.
The simple fact is that you are looking to replace a product that is effectively six years old (I consider Exchange 2003 to be a point release of Exchange 2000 - they are very similar), with one that is only a few weeks old. It needs time to bed in.
If the deployment of Exchange 2007 goes through without a hitch, then you are fine.
If you are having your spam and AV either taken care of by a third party service outside of your network, or you are going to use Microsoft Forefront, then you are also fine.
However if you have problems then you will be stuck. In the last 24 hours I have heard of two people who have taken E2007 issues to Microsoft Support who have failed to resolve them. They then come to newsgroups to get assistance and found none, because the knowledge just isn't there.
Exchange 2003 is very mature and there is an awful lot of assistance available for it in the form of newsgroups, forums and independent consultants. Most problems are well known, covered either in the Microsoft knowledgebase, blogs, forums, newsgroups or web sites.
For Exchange 2007, there are no books, very little documentation. Even the documentation from Microsoft cannot be relied upon at the moment. The help documentation is riddled with errors. I have sent a number of feedback items for errors in the help documentation.
(I suspect that soon I will be recommending that after installing your Exchange server, the first thing you should download is a new version of the help or at least ignore the help file that is supplied with it and rely on the one on Microsoft's web site.)
Then you get issues with third party support. Very little is confirmed to be working with Exchange 2007 (and don't take the sales droid word for it - they will say it is compatible with Exchange 4.0 if it will get them a sale).
The questions I ask of those who ask me about deploying Exchange 2007 now, is do you want to be the guinea pig for application support, be the one of the first to discover what does and does not work, and when you find things do not work, are unable to phone up an IT support company and get assistance?
What about administration? Your IT person gets up to speed on Exchange 2007 setup and admin, goes away for the weekend and breaks their leg. Getting someone to stand in for them at this time will be very difficult.
Therefore what I am suggesting to clients at the moment who need to purchase Exchange is buy the Exchange 2007 licenses then request an Exchange 2003 media kit. Use downgrade rights for the next six to nine months. Get used to Exchange, get it working how you want - as it is well known what is and is not possible with Exchange 2003.
In six to nine months time it will be much easier to transition to Exchange 2007. The product will be more established with many techniques which are taken for granted with Exchange 2003 are known and tested with Exchange 2007.
Third party tools and applications will have been tested, possibly updated with new versions. Those that don't work will be known and there could be workarounds or alternative products available to you.
What you should be doing at this time is building a lab. A separate domain, possibly using VMWARE or Virtual PC/Server. Get hold of the evaluation editions of Exchange 2007 and install it so that you can start to see how it works. As your existing vendors bring out applications that are compatible with Exchange 2007, test them in the lab.
When it comes to the transition to Exchange 2007 for production use, you will be very familiar with it and confident about using it.
Of course the only problem with waiting is that there is no in-place upgrade available for Exchange 2007. While new hardware should be 64 bit (with a 64 bit Windows 2003 license) if you are using Exchange 2003 you will need to have 32 bit Windows installed.
Therefore when it comes to the upgrade you will need to carry out a swing migration using another machine as a temporary step.
However for the potential disruption that you may have to email while Exchange 2007 settles down, that slight inconvenience of having to use a temporary machine for a couple of days later in the year may be worth it.