Finally(1) get working MPxIO with IBM disk array under Solaris 10 SPARC. Why don't we use IBM software included with the array? Well... let's just say it's bad, really bad and that's all you can really say about it. I must say I'm happy with MPxIO - it just works. To be honest it's not as good as EMC's PowerPath in terms of monitoring and some managing features. I really like PowerPath. On the other hand MPxIO is simple to configure and really easy to use, and while PowerPath is more powerful in many cases MPxIO is just enough and it does its primary purpose really good which is path failover and load-balancing. And MPxIO is for free - it's included with Solaris.
I must say that IBM's software included to manage and monitor the array is really bad, especially comparing to what I get used with EMC's software. I was expecting more from IBM - real disappointment.
(1) looks like IBM has changed Product ID of the array so MPxIO couldn't recognize it. Patch from Sun was needed - thanks guys for a quick response!