I live in California and I'm seriously considering switching to Democrat so I can vote in their primaries. I can still vote GOP in the election, if I choose.
I figure I can achieve two things; I might be able to help keep communist Dems off the ballot - AND I can send a signal to the worthless Calif. GOP party that they are losing voters.
I live in MD, and I was a registered Dem for the same reason. I finally recognized that was a bad idea here. First of all, I wasn't able to help the best GOPers get into the pipeline. And that's important. Secondly, the GOP Nat'l party doesn't provide much help to candidates in "hopeless" states (nor do I think they should), and counting as a Dem made it seem more hopeless.
Also, none of the Dem candidates ever were anyone I preferred to the others. I feel better voting for a losing GOPer than I ever did voting for a winning Dem.
Think twice before you change. Then a third time if you are still considering it. :-)