There are improvements in Solaris 2.x.
1) OpenWindows 3.3+ (in Solaris 2.3+). Includes X11R5 and Display PostScript. X11R6 in Solaris 2.6.
2) Motif & CDE.
3) ANSI-C and POSIX development environment.
4) POSIX threads (2.5)
5) POSIX and X/OPEN command environment
6) UNIX 95 conformance.
7) Posix shared memory and semaphores (2.6)
8) Multi-threaded kernel and real threads.
9) Real-time feature in the kernel
10) Faster clock ticks (optionally 1000Hz in 2.6)
11) Large files (2.6)
12) True multi-processing.
13) Goodies: vold, admintool and Wabi.
14) Easy patch installation/administration through installpatch.
15) All software in easy to manage "packages".
16) Power management software.
17) Access control lists
18) NFS Version 3 and NFS over TCP (Solaris 2.5+).
19) A better automounter, autofs (not more /tmp_mnt and symlinks).
20) Jumpstart/autoinstall.
21) Better MP support.
22) Faster networking (ATM, fastethernet).