My iPad 2 has been serving me well for a year and a half but I recently noticed it getting sluggish. More specifically, using Safari became like pedaling in hummus. Opening a new tab or selecting the Search or URL bar seemed to be consistently taking two or three seconds. I resigned myself to life like this for a while until I accidentally clicked the double arrow on the right side of the OS X Safari’s Bookmarks Bar.
It took a few seconds for my laptop to display all the entries. At that point I reasoned that my bookmarks, synced via iCloud, were causing the sluggishness. A trip to the Bookmark Manager showed that there were roughly 700(?!?!) first level items in my Bookmarks Bar, along with a dozen or so nested folders with a few hundred more items. I dragged nearly everything in to the Bookmarks Menu and it instantly solved the problem. I opened the iPad and the problem was indeed solved there as well, all was lightning quick again. Interestingly enough, the ‘normal’ bookmarks menu in both the OS X and iOS versions of Safari seem to have no trouble with a large quantity of links.
TL;DR – Too many links in the Safari Bookmarks Bar slows everything down.