Over the last few weeks I've been trying all the recent product demo's with some footage from my Panny SD5, I gave up on direct avchd editing last year and went back to mpeg2 as everything I tried was unstable and slow.
I went for Sony Vegas Movie Studio in the end although Adobe Premiere Elements 7 was a very close second (didn't seem quite as quick rendering the final output).
There's a good deal on the Movie Pro version (if you have Student/Teacher in the household) for
£59 on Amazon otherwise its £78 vs the Platinum at £57. The Pro version adds more visual effects, Sound Forge Audio Studio for better sound editing and Cinescore Studio for royalty free soundtrack creation.
If you have the time I would download the demo's of Premiere Elements and Vegas Movie Studio to see which interface you prefer.
I found Pinnacle Studio 12 to be fairly similar to my experience with last years version, buggy, prone to crashes and slower than the competition, of course YMMV - still its a bargain at £48 for the Ultimate version if you don't mind the hassle/thrill of wondering whether it will finish the render without crashing...