If you were an IT manager for a company, you would have to decide what IT systems to use so that everything works, so you might come to think about the following things:
1) Choosing an OS for desktop PCs
Currently Windows XP is probably the most functional OS, since it can run most of the available applications needed for most kinds of business.
It works perfectly in the 32-bit version, but the 64-bit version has problems with support and drivers.
In future, applications will need more than those 2GB of RAM which 32-bit XP can handle (+2GB in PAE mode with limitations for code and data).
Vista has much better 64-bit support than XP, but it wasn't accepted by businesses due to its high hardware requirements.
Windows 7 fixes mostly the hardware upgrade needs, but it brings a new problem: many Windows programs won't run on Windows 7, as they did on XP, and that would require businesses to redesign their software. That again might turn impossible, since in many cases there is no possibility to upgrade the software (developers have left, source code is missing, etc...), and it would easily be much more expensive than upgrading hardware.
The XP mode of Windows 7 is not much tested, and requires a seperate XP license also. From experiences with VM solutions, most people will agree that VM will have problems with some programs, which ran fine on the real XP.
Windows 7 might look much better with SP2, since from experience SP2 was the key factor which made XP and Vista usable, but since Windows 8 is probably coming out before Windows 7 reaches SP2, it might be a too long wait for most people.
Ubuntu seems to be the most downloaded Linux distro (IBM builds also their 2nd attempt of Linux on that), but that number comes also from the fact that it aims at total open source software. Businesses can't work with open source software only, as some key applications are commercial. Also the fact that Ubuntu's WINE can't handle many Windows applications, makes it useless for many people.
openSUSE is sponsored by Novell and Microsoft, and uses a hybrid open source/non-open source model, which allows it to enable access to much more software than Ubuntu. Not so surprisingly, many Windows applications run on openSUSE's WINE, which won't run on Ubuntu's WINE. I think Microsoft's support has brought some benefits to that, but it might be also just the fact that openSUSE handle's hardware better than Ubuntu.
Generally speaking, WINE runs about 13000 Windows apps, that's far more than Windows 7 runs.
Interestingly, WINE runs also high end 3D applications faster than Vista and Windows 7, but only slightly slower than XP.
Conclusion:
I would say, use XP as long as it works, and then upgrade to openSUSE.
2) Choosing the coorporate database engine
Businesses need to store data, a lot of data, and have instant access to all of them.
Notes/Domino provides a easy and functional solution for most businesses. It provides coorporate mail functions, collaborational file and rich text storage systems, and also business sales systems. For businesses with more than 1000 employees the price is around 20k per server, but you don't really need many servers. Domino lacks of SQL queries, but provides LotusScript to create superrelational queries. Generally superrelational queries are slower than bare SQL queries, but they have also no limits to what fields or data can be joined, so in the end they actually have prooven to be much faster than conventional SQL joins.
Oracle focusses mostly on business sales systems, and the price is accordingly high. You'd have to pay easily over 300k per database server. And you don't get rich text clients to work with, it's mostly just a bare SQL server, with some possibility to use OracleScript to make development faster and easier. Trying to make web based apps with Oracle makes no sense, as every other database can do it better, faster and cheaper.
MySQL is an excellent industry standard web app capable database engine, similar to Notes/Domino. Like Domino, it can serve also as a native database server, but it truly comes to power with web based apps, just like Domino. It's not quite as intuitive and easy to use as the Notes/Domino combo, but it has its own benefits. One benefit is of course that it's free and open source.
Conclusion:
Use Notes/Domino as base system, and Apache/MySQL for situations where it suits better.
3) Choosing the server OS and hardware
Windows Server 2003 R2 64-bit works fine today, and supports also more than 4GB of memory, which is essential for any kind of database server hardware. However, just like XP, it's getting soon old, and faces its end of support.
Windows Server 2008 has just like Vista and Windows 7, problems with existing Windows applications. For example Remote Desktop Connection to a Windows 2008 server will result in over 5 sec delays for each mouse click. Maybe it's fixed in SP2, but it's not confirmed.
Ubuntu Server has similar problems like Ubuntu Desktop with all kinds of harddrives or their SCSI, SATA interfaces. I tried to install on a fully intact new server hardware with Ubuntu Server, and it just didn't manage to put the physical harddrives in the RAID 10 array. It usually wanted to put cross-cable drives mixed up together, but it was rather a random behaviour.
openSUSE doesn't need a seperate version for Desktop, GUIs (kubuntu, xubuntu, etc...), Servers (Intel, PowerPC), or even consoles (PlayStation 3).
It also doesn't either need any derivates which improve, like Ubuntu needs Mint. It's just the one and only OS you need.
openSUSE is known as the OS with the fastest I/O in the world. IBM tried to challenge its I/O speed once with it's IBM AIX 6.1 OS, but they didn't come up to the same speeds. Also IBM AIX 6.1 for IBM's own PowerPC servers is not as good as running openSUSE 11.2 on those machines.
Conclusion:
openSUSE 11.2 is the perfect server OS. It has the fastest I/O, incredible hardware support, most modern Linux kernel. There's really no other alternative for any hardware, may it be Intel or PowerPC (pSeries, iSeries, PlayStation 3, Apple).