First of all, forget about whether the residence requirement is 5 years or 6. It was 5 until 2003; then they made it 6; now they are planning to make it 5 again. The difference is not essential in comparison to other things: when the required residence period starts, and whether or not it can be interrupted.
The law of 2003 allowed the possibility of interrupted residence: you can apply after 6 years of continuous residence, of after accruing 8 years of residence during your lifetime. The new one reduces those to 5 and 7.
More importantly: the law of 2003, and the previous one as well, counted as residence only A-permit and permanent permit residence - you could live all your life here on a B-permit and never be eligible to apply for the citizenship. (I won't do into A- and B-statuses here; enough to say that the student and temporary workers get B, and some of the permanent workers get B for the first 2 years.)
In 2007 a court found a bug in the law, and after that everything started counting as residence. This was in fact quite unprecedented: there are other countries that count temporary-status residence for citizenship eligibility, but AFAIK Finland is currently the only one that also gives citizenship to people still living on temporary status.
The new law is a compromise: it will count half of the B-status time towards the citizenship, but will allow people to apply for citizenship only after they got A-status.
That, BTW, is why I only got the citizenship now. I have lived in Finland for about 14 years, the last 8 of them continuously, but since I was a student, a temporary worker, and for the first 2 years of the last 8 a B-status permanent worker, I only became eligible to apply after the 2007 court decision (if not for it, I would only be eligible to apply 4 weeks from now).
Anyway, once the Immigration Service mentioned the court decision sometime it March, the rest was easy. I signed up for the language test. I cannot really comment on the level of the test, because instead of signing up for the medium level (the one for the people who want the citizenship) I signed up for the high level (the one for people with stupid macho tendencies who want to pay extra 45 euro or so and take a harder test for a piece of paper they'll never use). It had 6 parts of varying difficulty - more about it later. I got 6 (the highest grade) on every one of them. Go me!
With the test result, 400 euro and a filled application I went to the immigration police sometime in early May. Yesterday I got a letter with two pieces of paper. One of them said "you are a Finnish citizen now". The other said "go to the immigration police and have them cancel your residence permit, a citizen is not supposed to have one".