I'm in a very similar situation. I'm going to be attending University later this year to study computer science and along with a contract as a web developer, this means I will be spending money I can't really afford on expensive computer books, so just yesterday I was looking at the possibility of getting a safari account and drew up some advantages and disadvantages:

Advantages

• You'll have access to a large number of books: there are currently 1347 books available, from 14 different publishers, in a large number of different aspects of computing.
• With a starter account, each book you rent out will cost you about $2 a month, and with other account types this will work out to be even less.
• You can always upgrade your account type if you find you need more bookshelf space than you originally anticipated.
• Safari has quite a nifty little search engine that allows you to find answers to questions fairly easily
• You can cut and paste code examples instead of copying them from the book
• You don't need large shelving units that can hold all those heavy books :)
• It's cheaper to rent large amounts of books than it is to buy them all, especially when you may not extensively use some of them.
• You aren't left with redundant copies of books when texts get updated.

Disadvantages

• Safari is an electronic reference library, not an offline viewer. It assumes you have a reliable, unmetered and readily available internet connection.
• The only acceptable payment method currently is by credit card, and only certain international credit cards are accepted.
• If your interests lie in one specific area of computing, e.g. Perl, Linux, then in the long term it is cheaper to buy a CD bookshelf or hard copies of books then it is to subscribe to safari.
• If you are lucky enough to live near a well stocked local or college library then you can loan out the books for free.
• Safari uses detection software to prevent people from using spider software to download entire texts. This isn't entirely foolproof, so you may find yourself being logged off or have your account suspended for otherwise innocent behaviour like fast reading safari books.

In conclusion, I think that a safari account subscription would be a good idea if you require to have access to a number of different fields of computing, some of which you may only need to dip into briefly for a specific task. However, if you only work in a specific aspect, say Linux or Perl, and use books as a constant reference that will always be found lying on your desk, then it's cheaper in the long run to buy a paper version or something like a CD bookshelf. Or maybe do a combination of both a starter safari subscription and have a couple of well thumbed through manuals :)

I hope this helps!

--
Rozallin J. Thompson
The Webmistress who doesn't hesitate to use strict;