As long as you own and are responsible for what you are supposed to be doing and deliver on the commitments made you are free to manage your time as you see fit. In reality, it's a team decision and not the decision of the boss (me, in this case). If someone wants to go out of town to see a concert or take the kids to Disneyland for a few days, we talk about it. More often than not there are no issues and the answer is "send pictures". Sometimes the answer is "OK, but could you take the laptop and see if you can finish this little chunk of code". When it can't happen it is obvious to everyone.
Want to take a month off to go down to Argentina? Let's figure out how to do it. You might have to drag along the laptop and keep up with some stuff, but there are probably few reasons to say no. Can I come?
The same applies to sick days or "personal" days (who came up with that term?). You are sick? Please go to the doctor and stay home? Need to go take care of that speeding ticket? Take the day if you have to.
This also applies to work hours. Sometimes you have to put in the time to get something done. When discussed as a team these instanced become self-evident.
I said in another post that I am no stranger to 18 hour days. I hate doing it, but sometimes you have to. In all cases this kind of thing must be fully justified. It can't be the norm. If it is, something is seriously wrong or you need more people.
9 to 5 programmers have one guarantee: They will work 9 to 5 every day and will be held to strict rules when it comes to vacation, personal and sick days. If you want to work a strict 9 to 5 schedule I have to treat you differently. I have to treat you by the letter of the law. So, while the guy/gal in the other plan is in Argentina having fun and doing some coding, the 501'er will be clocking in and out and accounting for meal time and vacation days. Yuck!
I, personally, hate that kind of work accounting. Not for me. To each his/her own.