The best replacement for updatepanel is panel.

The best alternatives to updatepanel are rated as following:
★★★★★  panel
★★★  pagemethods
★★★  radajaxpanel
★★  callback
★  panel asp.net
★  callback panel
★  aspxcallbackpanel
★  xmlhttprequest

Your alternative for updatepanel is not listed? Suggest!
Speaking about updatepanel, one probably shouldn't forget about modalpopupextender.

Other search terms related to updatepanel and their ratings are:
★★★★★ modalpopupextender
★★★★★ dropdownlist selectedindexchanged
★★★★ tabcontainer
★★★ viewstate
★★ progress bar
★★ scriptmanager
★★ loading image
★★ fileupload
★ ajax
★ postback
★ user control
★ fileupload control in asp.net
You have in mind a companion for updatepanel and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of updatepanel in all years. Click on graph for more.
updatepanel
panel
pagemethods