When talking about HTC phones, most users mention "HTC has HTC Sense" without much elaboration (cannot blame them because of my noob-ness). Tried to google it but got a wikipedia page that pretty much says it's a UI for HTC.

Q: What's so good about HTC Sense and how it relates to Android OS?
Q: Is HTC Sense really a factor in deciding between HTC and other phones (e.g. Samsung)?