Finder slow after wake up from standby mode
The delay occurs because Finder is remounting each share, (I would guess sequentially, not concurrently, but I'm not sure about that,) and that always takes a few seconds per share, if not more, depending on the server and network conditions.

I think you will be happier if once the shares are mounted you make Dock items for them instead, and not use the sidebar.

NOTE: even if you use the Dock method, shares already mounted when the Mac is put to sleep will need to be remounted once the Mac wakes up. You might want to dismount the shares manually before putting them to sleep, or purchase the app Jettison from the Mac App Store.