I don't use it much and tend to only use it when I'm particularly familiar with someone. Find it a bit odd when I'm not so familiar and people use mate left right and centre.

Usually don't like it when people use overly familiar terms in general. I deal with sales people daily in my job and get it more than I'd like (nj). Got a particular customer service guy who calls me Pal, Chief, Boss, Mate, Bro. Gets right under my skin.

I guess I probably should just chill out a bit.

I know what you mean, I think it works in peer groups, so give a feeling of solidarity among colleagues, but for 3rd parties, sales people etc, it's used as a way to ingratiate themselves on you.