iTunes now takes up 100% of CPU since updating to 11.3 UPDATE:
The issue seems to be at least related to what konqui mentioned in the Comments since I do have a large library of podcasts. However, if this was merely related to re-indexing then one would expect things to go back to normal but this doesn't seem to be the case.
Basically, now everything (related to podcasts, at least) takes about 100 times longer than it should take. For instance, after clicking on the podcasts tab itself, it takes 10 seconds (with CPU at 100%) and just refreshing podcasts has taken up to 30 minutes.

Since updating iTunes to Version 11.3, it quickly takes up 100% of the CPU and stops responding every time I try to open it.
I've tried:

Waiting for it to sort itself out on its own
Force Quitting (and then re-starting iTunes)
Re-starting my computer entirely (MBP, running Version 10.9.4) and then trying both previous approaches.

Has anyone heard of this issue before? Should I uninstall 11.3? And, if so, how do I do this?
Again, this problem has only started happening since updating to Version 11.3 two days ago.
Another strange thing is that iTunes does not appear to be totally frozen--for a few seconds the &quot;(not responding)&quot; will occasionally disappear and then reappear. Plus, in those few seconds that it starts to respond again, its status will change (for instance, now it says it is &quot;Processing Album Artwork&quot; and earlier a random podcast started playing). However, this doesn't seem to explain why the % CPU consistently remains at around 100%. [UPDATE: The 100% CPU/&quot;Not Responding&quot;-status may, for some reason, be related to podcasts being refreshed]
Currently, the only Applications I have open are:

Activity Monitor
Google Chrome
iTunes
Finder
Since upgrading to iTunes 11.3 I have experienced a very similar problem.  Every time I refresh my podcasts, iTunes' memory/CPU usage surges, and the iTunes UI freezes up for 5-10 minutes.

I haven't found a complete solution, but I have stumbled across a temporary workaround.  On my system, the problem only seems to occur when I refresh podcasts while looking at them in the List view, as in the screenshot below:



If instead I refresh podcasts from the All Unplayed view, there is no freezing at all:



It appears that the issue is related to viewing the podcast list while refreshing all podcasts.  (You can even avoid the issue if you click refresh in List view and then quickly click away to another view, like Music.)

Not a super satisfying answer, I know, but for me it has returned iTunes to a semi-usable state.