(Edited copy of review posted for v.5 - but relevant to v.6)
I originally bought Anime Studio Pro v.5 and then upgraded to 5.6 free of charge via the official website. With the advent of v.6 (already upgraded to 6.1) you might be able to find v5 very cheaply and if you're just starting to experiment with animation and characters that can use 'bones', I'd strongly recommend looking for it.
However, the latest incarnation in v.6 IS a big step forwards as it offers a much wider range of controls, functions and possibilities - even if the job of developing the software still does has quite a long way to go. Nevertheless, with experience, very professional animations are possible. You should be aware that the learning curve is fairly steep - but the available tutorial packages are a great help.
There are three things that I would really recommend:
(1) Only consider the 'Debut' version of ASPro v.6 if you are really strapped for cash - the full version is the one to get .... or you could try to find v.5 as I originally commented.
(2) Before you decide whether or not to buy, I strongly recommend that you browse the official 'Anime Studio forum'. (Search using that 3-word keyphrase and you'll find it straight away.) You will find masses of information and opinions from both new and expert users there.
(3) Having said that, as ASPro evolves, functionality and compatibility issues with v.5 and 5.6 can only become more problematic .... so it's up to you, but if you're unsure, I'd definitely recommend browsing the free forum as mentioned in (1).