I want to apply to PhD programs in English Literature this December. I have pretty good stats from a good liberal arts college + summa thesis, but I majored in Russian Lit. I took a couple of English classes in college but I probably won't do very well on the GRE subject test in British/American lit. Is it possible to get into a PhD program with a good all-around application but bad subject test scores? Should I address my lack of canon-knowledge in the personal statement or leave it be?
The OP is asking about the GRE subject test in English, not the GRE general exam. The verbal score for the general exam is arguably relevant, and I can say for certain that the subject test score is definitely important.
This question was asked a year ago as I write this, but for those who see it in the future, I would recommend using a test prep book or similar to do some crash studying for the subject test. I took it twice, myself. The first time, with no such preparation, I got a 530. The second time, after reading the Princeton Review book, I scored a 680 (above the 90% mark, in percentile terms, which is more important than raw score). Both scores were reported to the schools I applied to. Someone at the one I ended up going to told me they were impressed by how quickly I was able to increase my score. I was impressed by how little this test must actually mean if I could just flip through a study guide and practically nail it. This was in 2001, by the way. Things may have changed. But I doubt much.
I should add that I was, in fact, an English major. But I didn't have broad exposure to all periods and studied very little theory as an undergrad, so I was in the dark in that respect. The Princeton Review guide was very good at getting me up to speed on material likely to be on the test (as well as offering a useful test-taking philosophy). It's better and more efficient than reading the entire Norton Anthology, that's for sure.
You have to realize that the top programs in English receive in excess of 300 applications a year, maybe more, for annual classes of a dozen or so students. To say that the GRE isn't important is suggesting that overworked members of admissions committees aren't looking for any excuse to trim the pile, which in fact they are. Everything is important.
Just like in the sciences, the GRE is not particularly important for admissions to humanities PhD programs. That said, the GRE can be used as a tool to decide who gets the limited funding and the most desirable TA positions. As for the personal statement, you need to address why you want to switch from Russian Lit to English Lit. In fact this should probably be the core focus of the personal statement.