I just removed my Candyshell and ran a little test on mine. For the record, my coverage has always sucked here at work.
Started with three bars. Opened Safari and selected my bank website from bookmarks, waited for it to start loading and placed my thumb over the seam. Immediately the progress bar froze, bars dropped from three to one to searching, popup tells me it can't load the page because there's no internet connection. Release thumb, hit reload, bars climbed back to four and page loaded fine.
Second round I selected Macrumors. Bar progressed pretty quickly but again immediately froze when I put my thumb on the seam. Bars again dropped away to searching in less than ten seconds.
Seems I'll be keeping my Candyshell on.