I have just read http://www.chessbase.com/newsdetail.asp?newsid=2340 . 
So, for each new move he saves that particular position.
If I were to create my repertoire against e4 in such way this would result with hundreds of games (or even more) in game list. (and I actually don't even play openings that are too theoretical)

Of course I could only add about let's say 10 basic positions to the game list and then insert detailed variations inside them but this isn't really practical, and doesn't recognize transpositions. (It's also not the way it's taught on the web)

To me, Chess Position Trainer is much easier to use, and not only that, it's also much faster and more practical. You simply enter all the moves of variations you play (you can also insert evaluations, comments, etc.) and the program automatically recognizes the transpositions.
You can also train your opening knowledge by playing against it - it's a very nice way of refreshing the knowledge before a game.
You can also compare the games you have played online with your book and the program checks where you or your opponent played the new move.
I guess you could also ask the program to analyse newest games (from TWIC for example) to check where someone played a move which is not part of your book. And, of course, if the important novelty occurs you can easily add it to the book. But this should only be relevant to those who play fashionable openings.

So what are the advantages of creating book with Chessbase 10 then with Chess Position Trainer? Hopefully someone who knows both programs well will be able to tell me!

I use Chessbase 9 to maintain a Repertoire DB. It wasn't intuitive at first, and a bit tedious to get the the lines in, but it's easy to maintain once set up. 

I like the Generate Repertoire function (under File->New oddly  ).

e.g. I can grab say a TWIC update, a Chess Publishing games file or a Tournament games file, run Generate Repetoire, and see all the games that fit my repetoire. Any that look interesting I can add with a Right Click-Add to Repetoire. Easy  . Annotations go in too.

Also if I come accross a player that plays the lines I like, I can seach on their games and do the same Generate Repertoire on it to add them to mine in the same way. 

Also if you select a game in your Repetoire DB and choose File -> Print -> Print Repetoire, you can get pages that look like, e.g. NCO format.

Damn. Now I have to learn something besides chess, too...
But I guess I'll be happy with the result, my opening analysis right now are in total mess. (and/or scattered in a few books)

MilenPetrov wrote on 01/04/09 at 22:49:39:

Will these links be enough to learn what you have learned from that book?
http://www.chessbase.com/newsdetail.asp?newsid=2340
http://www.chessbase.com/newsdetail.asp?newsid=2341
http://www.chessbase.com/newsdetail.asp?newsid=2342

Thanks guys. 

Both of your suggestions are great. I'll stick with ChessBase 10 with Mega Database 2009, but CPT is a nice way to create a repertoire, too.

ChessBase 10. The best chess program on the market. It also comes with Big/Mega Database 2009, ensuring that you are fully up-to-date and can check/expand your opening knowledge.