You can manually map the MPxIO names against logical unit numbers with luxadm, see the size with format or iostat and find used disks with zpool status, mount or some other. This does require many different commands and you will not get all the information listed in once place.
A while ago I wrote a utility to collect and present disk information in Solaris that I called dskinfo. It relies heavily on existing commands in Solaris and parses their output but have worked very well for me in many different environments.
This initial version is best suited for systems using ZFS since it can only show the usage of disks part of a zpool (exported or imported). It can still be used to get a summary of all disks on the system and later version might add additional filesystems and volume managers as well. I have labeled this version 0.9 and I will use feedback to create a 1.0 version before I look into adding more functionality.
dskinfo displays disk information with four subcommands: list, list-long, list-full or list-parsable. The two first commands will output data on a single line with different number of fields, list-full will display all data on two lines per disk and list-parsable will display all data on one line with fields separated by a colon.
I have tested dskinfo on Solaris 10, Solaris 11, OpenIndiana and Nexenta with both local, iSCSI and fiber channel attached disks.
Example, I have only included the shortest type of list since the formatting here makes the other look terrible, they all look good in 80 columns:
$ dskinfo list
disk size use type
c5t0d0 149G rpool disk
c5t2d0 37G - disk
c6t0d0 1.4T zpool01 disk
c6t1d0 1.4T zpool01 disk
c6t2d0 1.4T zpool01 disk
A better formatted text file with additional listing options can be viewed here: dskinfo-example.txt
Please let me know if you find dskinfo useful or have any problems, I will try to fix them when I have time.
Version 1.0 is available for download here: dskinfo
Update: Version 1.0 is now available, it contains bug fixes, warning if SVM is used or VxVM is installed. It can also output driver and instance names and tries harder to acquire the serial number from disks. A quiet options is also available to remove warnings.