Take for instance web performance. We have improvemed 2 CPU performance by close to 50% (compared to Solaris 9) using a real web server like Apache, Sun One Web Server, Zeus, etc without any gimmicks like kernel caching etc. Its just plain webserver with TCP/IP and a dumb NIC. Some of our Solaris express customers are telling us that we are outperforming RHEL AS3 by almost 15-35% on the same hardware.
Interested in more numbers - On static and dynamic webbench, Solaris 10 is at par with RHEL AS3 on 2 CPU v20z while its ahead by 15% on webbench Ecommerce benchmark. On the same box, we can saturate a 1Gb NIC using only 8-9% on a 2.2Ghz Opteron processor but the real killer deal is that our 10Gb drivers are coming up and Alex Aizman fromS2io just informed me that we are pushing close to 7.3Gbps traffic on a v20z (with 2 x 1.6 Ghz Opterons) with more than 20% CPU to spare. We haven't even ported the driver to the high performance Nemo framework or enabled any hardware features as yet. So I am expecting a huge upside in next 2-3 months as the driver gets ported to Nemo (Paul and Yuzo should tell you more about Nemo sometime soon).
The improvements are not restricted to TCP only. We are doing a FireEngine followup for UDP which improves Tibco benchmark by 130% and Volano Mark benchmark by 30%. The customer tells us that we are outperforming RHEL AS3 by almost 15% on the same hardware. Adi et. al. can add some more details about UDP performance.
And the big killer features on Opterons, you can run 64bit Oracle or webserver on 64bit Solaris to take advantage of the bigger VM space but leave bulk of your apps to be 32bits which run unchanged.
I am not claiming the best performing OS title (atleast not yet!) for Solaris 10, but guys, we are still ramping up! Every new project going in Solaris is now delivering double digits performance improvements (FireEngine architecture has opened the door) and soon I will claim that title :) I must add that all these gains come on the same hardware without application needing to change at all. Just get the latest Solaris Express and see it for yourself.
And BTW, most of us at SUN are really pretty friendly towards Linux. Sure we compete in a good natured way. And Tom did hit the nail on the head regarding why people at SUN don't like Red Hat - Its really has to do with them having transformed free Linux into a not so free Linux.