Pocket Internet Explorer (Pocket IE) should really be called Internet Explorer Mobile or IE Mobile. I'm still in the habit of calling it Pocket IE (that's how long I've been using Windows Mobile)
The refreshed version of IE Mobile in Windows Mobile 6.5 is a considerable improvement than the browser found in 6.1, but I still prefer using either Skyfire or Opera Mobile. I'm eager to see Firefox Mobile (Fennec) when the final release gets out there. The refreshed version of IE Mobile allows you to zoom in and out of web pages much more effectively. Since the majority of Windows Phones use resistive touch screens (passive) as opposed to capacitive touch screens, we won't see any multi-touch gestures that allow you to zoom in and out by pinching or spreading your fingers in the current generation of Windows Phones.
So, if the one major benefit of upgrading from Windows Mobile 6.1 to 6.5 is to get the newer, more functional IE Mobile. Is that a real benefit if you're already using Skyfire or Opera Mobile?