According to the latest post on the Official Google Reader Blog the feature I spotted yesterday is now live; new/unread message counts now go to 1000 instead of 100, so you will no longer see 100+ on your tags. If you see 1000+ on anything other than your All Items folder then you probably need to unsubscribe from some feeds or reconsider your strategy for reading feeds.
The other new feature that has been added is a search that you can use to search all your subscriptions. I know many have been asking for this and it should prove most useful.
craniac's place 