Before I moved here on a Tier 4 visa, I had four visits to the UK to see my boyfriend. Twice in Manchester, once into Birmingham and once into Heathrow. I was grilled only on my first and fourth visit. Interesting to note that my first and fourth visit IOs were females while the second and third visit IOs were males. In my experience, I do think that males are easier to deal with/friendlier than females. I had the easiest entry when I came here on my visa. I showed my offer letter, was asked 2-3 questions, and in and out just like that.
BF has visited the US four times in the past four years and has said that US Immigration is ''horrible'' and very rude. I've flown back into the US through Newark, Chicago, and Atlanta and haven't encountered any problems at all. It's more of a ''welcome home'' thing.