As you know there are a lot of variables on this matter. It really depends on what content you have on the page and what scripts and styles it requires. Also the Script combining diminishes the server calls which surely helps server performance.
Also its worth mentioning that each combined .axd file corresponds according to the assembly it refers to. For example if you have content on the page that uses 3 assemblies you will get 3 .axd files with combined scripts from the corresponding assembly in them.
Another thing to add is that the Script combining can really be sensed by the backend users since the backend uses alot more scripts than an ordinary site.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items