I don't think it's a good idea to take the October exam with the mindset of "oh well I will just take it again in November". I remember it took about a month for me to get my PGRE scores, so you won't have much time, if any, between finding out your October exam score and your November exam date. Actually I just checked online for the score availability date: http://www.ets.org/gre/subject/scores/get/
You won't get your October score until after the November test.
It's a lot of money to take the exam twice, and it will cost you yet more money to send scores from a selected test date (see point below). In addition, one extra month isn't going to be that helpful in improving your score. Personally, I would not think this was a good use of my money or time, but you might have a different opinion!
As for scores -- when you register for the test, you can select 4 "free" schools. You can change/choose these schools up to the Friday before the test by mailing in a form. The GRE scores will be automatically sent to these 4 schools and your undergrad school for free after the test unless you cancel your score when writing the test (but you won't know your score). But, if you don't select any of the 4 schools and uncheck the "send scores to my undergrad school" box, you will be able to see the scores online or by phone. You should do the same for your November test, then after you get both scores, you can order additional score reports (~$20 per school) and use the new ScoreSelect option to pick your best score. So, even more expenses. (See http://www.ets.org/gre/subject/about/scoreselect
It also sounds like you are implying that you don't think you can take the test after knowing your score, but that's not true! You can take the test and see scores as many times as you want, but if you use the free test score option, all the schools will know your scores too.
It's better to take the test in April and Oct/Nov if you really want to do a "practice run" or have a second chance if necessary. But if you are applying this winter, then obviously this is not an option for you. I would recommend NOT using the 2008 practice test to prepare/study and then write the 2008 exam in "test conditions" about 2-4 weeks before your test date to simulate the experience. I recommend taking the time to fill out all the bubbles for your name, testing number etc. too just to simulate things exactly.