MTS CONVERTER  I tried Avchd MTS converter, this really worked for me... http://www.avchdmtsconverter.com  
(Version 1.8.2)

STSCHULTZE  For me this app is the only way to convert the AVCHD-format of my Canon HF100 in HD to an editable format. Still I don´t have an Intel Mac and will stay on my machine with power pc processor.

After testing it I decided to buy the app and now its simply a part of my workflow for high resolution editing. Even when I moved from my old G4 to a more recent G5 PPC the developers answered my questions very fast just in time. Its the way I like it - small but god money for simply working software. Without that app I could simply forget using my Camcorder with OS X. Thanx a lot for that, thumbs up  
(Version 1.8.1)

M85  FCE can only import SOME avchd. For instance, I've been trying since last fall to get it to import AVCHD from my brand spanking new Panasonic HDC SD100. It can't. Period. Final Cut Pro 6.05 can and iMovie '08 can (though I'm having audio sync problems with the iMovie and it converts 24p to 29.97 when it imports).

Anyway, I hope Apple updates FCE soon, but until then Voltaic is your best bet. MPEG Streamclip won't import mts files either, by the way.  
(Version 1.8.1)

LEIFH  final cut express can import avchd as of version 4  
(Version 1.4.1)