It is far too early to say. Ive had every version and Ver 9.4 was so stable that I didn't bother to install 10+ until ver 10.5 update was released
10.5 is Ok .. 10.7 worked for some not others
Avid have taken over Pinnacle and I don't get the Preview copies anymore ( at least not ahead of release) but I cant help feeling that Vista support and AVCHD editing ability ( as a well as HD-DVD authoring) are the major pluses for 11 over 10) .
If you are happy with it I would visit the Pinnacle forums to see what the problems ( or not) the new users are having as Pinnacle Studio seems to have a reputation for getting rushed release and then gets more mature with update patches
This may no longer be the case but ver 10 (which was supposedly built on Editions engine) had a patch released within 2 weeks of launch

!
In addition to Studio ( used a lot less now though pretty handy for some of those Hollywood FX) I also have Sony Vegas7,( and Movie Studio platinum 6 ) Adobe Premiere Elements 3 and Ulead VS 10 plus for use in addition to Avid liquid 7.
If Pinnacle Studio works for you and you are used to its interface..you'll find that although capable of quite stunning results, Sony Vegas Movie Studio and Adobe Premiere Elements have a slightly steeper learning curve. Movie Studio is only Vista compatible in ver 8 ( yet to be released)
I have used Premiere Elements 3 with Vista but not extensively enough to give it the all clear
HTH