A person can claim to be of one party, and in general, stand with that party on a number of issues. Not all candidates agree, however, and that is why we have primary elections. Primary elections are held to figure out who most closely represents the party as a whole. This implies that a candidate can also stand in opposition of their party on some issues.
If the issues that are important to you are not the issues that are important to the party you've chosen as a whole, but the other party's candidate does hold a stand on that issue and their stand is in line with what you think, you have a choice. You can, heaven forbid, pick up a phone and call your parties candidate and ask them for clarification on their stand.
If they agree with your view also, great. Vote for them. If they don't, perhaps you should vote for the other parties candidate.
If you can't talk to them for any reason, skip that last step and just vote for the other guy. You already know his stand and you're happy with it, so why vote for someone else who might not agree with you?
Now for the issue with voting a straight party ticket. What if the congressional candidate for your party agrees with your views, but your gubernatorial candidate does not? What if the other parties gubernatorial candidate's views are better than your own parties candidate's views? In this case, you're better served voting for your own parties congressman and the other parties governor.
Anyone hwo declares they're just going to vote a straight party ticket obviously hasn't taken the time to think about any of the issues that are important to them, and if they're not willing to be involved in stuff that's important to themselves, they shouldn't be injecting themselves into and screwing up things for the people who do know and care about issues important to them.
In short, if you're choosing to vote a straight party ticket because you like the party, you shouldn't be allowed to vote.
If your choice candidates that you're voting for all happen to belong to the same party, fantastic.