I am running PD 8 more than two years, and (after few patches and some tricks) I am satisfied with it. There were 2 (for me, important) issues, which had not been solved in PD 8:
1. Poor quality of produced DVD movies (no matter SD, HQ or Custom).
2. Useless Menu Designer.
Few days ago I decided to try TRIAL version of PD 10. Here I will not talk about problems with "unsupporting H.264 hardware encoding/decoding" (you can see thread
http://forum.cyberlink.com/forum/posts/list/21753.page), about old (already solved in PD 8 ) bugs, about new bugs, etc... I think it will be solved in near future. Here I will talk about "my" two qustion.
Unfortunately, answer is:
1. Poor quality of DVD (bad downscaling of high quality video and photo - you can find this thread in PD 8 forum) still REMAINS.
2. Menu designer is still useless, but I am shocked that this (BTW, the weakest part of PowerDirector) is absolutely equaly as in PD 8!?!?! Problems with "zombie" and choppy sound, with menu items, with scenes, etc...
From the other hand, I didn't find any improvement in PD 10, except 3D, which I even didn't try (I am not using it). Maybe, it's a little bit nicer, a little bit more comfortable... Here I've found similar opinions
http://forum.cyberlink.com/forum/posts/list/20400.page .
So, MY verdict is: I will stay with stable, good, and workable PD 8 (so far), and check regularly for new versions.