It often implies that you are "shattering" something the other people believes in. I don't think it's necessarily just a way to tone down your comment, but it can be a bit snarky as well. It indicates that you find the other person naive due to the views he has expressed. It's not just that you disagree with a particular comment, but you're quite convinced that the other person isn't able to discuss matters within their proper context ("I'm sorry, but that album isn't jazz at all", "I'm sorry, but validity doesn't mean that in philosophy"). So it can have a belittling tone to it as well. The way it is used can vary from person to person, of course.

Oh yeah, I use that sometimes. It's just a way to start a sentence, comparable to "apparenly", "for your information", "as far as I know" or "oh yeah".

Arnotts said:

It depends on why you're saying your opinion. If someone asks what you think of something like 'Is this dress ugly?' then its perfectly acceptable to say I'm sorry in front of the answer if you dont want to offend them but they want an honest opinion. If you are saying something because you want your opinion thrusted out there then yeah, you're not really sorry and shouldn't say so.

Totally disagree. The fact that someone asks, "Is this dress ugly?" creates a set of unspoken rules, the main one being "I want you to be honest - I'm asking for the truth, so go for it". The question was not "Is this dress ugly - and please don't hurt my feelings on it because I'm really attached to it, but I'm asking just because I'm not totally sure, please remember I'm a basket case."

What they're really asking is either "Should I spent the money on this?" or "Do I look good in it or not?" I've found in those type of situations, I say, "You know what, it's not very complimentary to you." It puts the "blame" on the item, not the person.

I'm a hair stylist and people ask me all the time about changing hair color. When I KNOW it's a bad choice they're thinking of, I'll say the same thing. "I don't think red is going to be very complimentary to you." Totally lightens the load on both ends.

In the end, the person didn't make the dress. Someone else did. So if your pal picks it out and then says "Is this ugly?", then why not just say "Yeah, it's kinda wacky!" or whatever? I made the same point above with people hating a Prince record. Prince ain't on here asking "Do you like my latest?" So why be "sorry" when you give a differing opinion to someone?

[Edited 8/9/10 7:13am]

Easy

"I'm sorry, but..." means : "Hey, I hate to say the truth, and I know that this is gonna upset you, but I have to say it anyway...you're a jerk!"