I think you will find that most all of the major players in 8th scale are rumored to at least have a significantly updated if not new buggy coming out in the next year or so.  I would guess partly because the worlds are this year, and partly because there is just alot of change going on right now in 8th scale racing.  The other crazy part about picking a buggy is that there are 7 or 8 really competitve buggies out there right now and all are pretty could competitors.  The difference of course being the differences in driving style.  The Mugen and Jammin are still some of the easiest buggies to drive yet still very competitive.  The durability issues with the Associated buggy are all but fixed, but it still needs some ironing out overall.  Its a tough choice right now primarily because there are so many good kits to choose from.  I would start asking people what it is that they like about there buggies and try and determine which one fits your driving style best. 

Hope that helped a little..

Trent