Evgeniy,
Watch out on this man. We also did SPNEGO for Solman, but we ended up turning it off and just doing SNC for the SAPGUI.
We found that it broke some of the monitoring tools, the way that satellite systems communicate with Solman and the way solman talks to them.
Jobs just started failing, and the config screens inside solman just wouldn't work.
I still like SPNEGO,SNC, but for solman, really there isn't any point for us if it breaks those monitoring tools. It would be too difficult and time consuming to explain to SAP support for a fix. I have put in enough solman tickets to know it would just bounce between solman support and SSO support and it would waste time.
For our end users in solman, they use SAPGUI so just enabling SNC was good enough.
You could always do X.509 for others if they hit HTTP(s) connections to solman. So that's what we've done, but we didn't use SAP secure login server. We just did it internally.
NICK