Lightroom 4 on sale for $100 in US

Hi,

I've been thinking about LR since IDImager has changed their practice. But, I've seen some criticism that LR 4 runs slow. Some say it slows down the more you use it (Maybe as the size of the data base grows?).  Any experience with this problem ?  BTW I have a core2duo 2.13GHz and 4GB RAM.

Thanks,

Bob Schoner