[fintstone]

Generally, filing joint is the best for most folks.

The place where making more (adding spousal income) can be disappointing is if you have deductions or credits that are limited by income. Contrary to popular belief, those making more usually get screwed because they lose a lot of credits/deduction because they make too much and many deductions/credits are simply thinly disguised social welfare (or the ceilings are poorly disguised punishment for working smarter and harder depending on your viewpoint). Either way, making more is always a good thing as you next raise is generally dependent upon your last and rarely do you lose money long term.

Here is an example of one (a credit) The text below lifted from the IRS:

...The American opportunity tax credit (AOTC) is a credit for qualified education expenses paid for an eligible student for the first four years of higher education. You can get a maximum annual credit of $2,500 per eligible student. If the credit brings the amount of tax you owe to zero, you can have 40 percent of any remaining amount of the credit (up to $1,000) refunded to you.

The amount of the credit is 100 percent of the first $2,000 of qualified education expenses you paid for each eligible student and 25 percent of the next $2,000 of qualified education expenses you paid for that student....

What are the income limits for AOTC?
To claim the full credit, your modified adjusted gross income (MAGI) must be $80,000 or less ($160,000 or less for married filing jointly).
You receive a reduced amount of the credit if your MAGI is over $80,000 but less than $90,000 (over $160,000 but less than $180,000 for married filing jointly).
You cannot claim the credit if your MAGI is over $90,000 ($180,000 for joint filers)...."