Seeing O'Brien is always a treat. I liked how the aliens looked alien and not just some facial bump (Worst case of that coming in Symbiosis).
The plot with the entity is... mediocre at best. I thought the crew should have acted a little sooner with Picard giving out phony commands and the resolution in rescuing Picard came off as anti-climactic. I just didn't get it.
Also, doesn't the Enterprise-D come equipped with probes? Why not just leave a probe in the cloud and gather the results at a later time?