Microsoft has nothing good to say about Oracle's upcoming purchase of Sun, with Steve Ballmer himself coming out to say that he doesn't understand why a software company would buy a hardware company. There are also opinions that the deal would only serve to boost Microsoft's position. The reason being, Oracle will soon become a hardware vendor that will directly compete with big companies like HP, who may no longer want to push Oracle's software. From either point of view, it seems Oracle would be losing out.
The Linux Foundation, on the other hand, sees the acquisition as a positive change, citing Oracle's support of Linux in numerous fashions. Some have cited the potential conflict of interests involved, as Oracle will soon gain control of Solaris and Java, two platforms that can stand alone on their own. However, Jim Zemlin of the Linux Foundation doesn't believe that this will result in Oracle reducing support for Linux, but rather in more customer choice.
Ultimately, it does seem that Oracle will have a much larger collection of tools to offer the enterprise - on top of the well-known Oracle database which primarily competes with MySQL. It also gives them a better streamline to offer a full solution, hardware and software, to businesses. Are Microsoft's words more out of fear that they could stand to lose customers to a more potent Oracle?