1) How much can one truly understand the sensory world of an invertibrate? There must be some limit to which the experience of a human can be mapped onto that of a lobster. Both probably have a sensation that informs the brain to avoid that which caused the signal, but it is fundamentally impossible to compare the experiences. There might be a way to compare the processes, but I don't think that anyone has found a way to get a conscious lobster to sit still for an MRI.
2) The science has gotten messily political on this issue. A quote from a spokesperson from PETA was sited thusly:
PETA's Karin Robertson called the Norwegian study biased, saying the government doesn't want to hurt the country's fishing industry.
"This is exactly like the tobacco industry claiming that smoking doesn't cause cancer," she said.
Robertson said many scientists believe lobsters do feel pain. For instance, a zoologist with The Humane Society of the United States made a written declaration that lobsters can feel pain after a chef dismembered and sauteed a live lobster to prepare a Lobster Fra Diavolo dish on NBC's "Today" show in 1994.
So on one hand, the Norwegian study is biased and can't be trusted, but we can trust a Humane Society scientist's word on the issue. Evidently Ms. Robertson distrusts economic bias more than ideological bias. At least when the bias is of her ideology.
3) Got butter?