It really used to be so nice until Google got their grubby hands on it. Nowadays I can barely get through a single video without massive stalling issues, or 30 second ads for a 10 second video. It's ridiculous.
The massive stalling issues are probably a result of your ISP. I know that Comcast massively throttles YT video downloads after the first thirty seconds or so of the video have been downloaded. (I've verified this by directly downloading a particular video file at home, and at a Uni across the continent. The download at the Uni downloaded at maximum speed until the rather long video was downloaded.)
It really used to be so nice until Google got their grubby hands on it. Nowadays I can barely get through a single video without massive stalling issues, or 30 second ads for a 10 second video. It's ridiculous.