My ride buddy has an '04 X, and after one ride on my '05 CCC X, he had to make the conversion. On both bikes, I've only used '05 R parts where they differ from '04 R parts (cam and header). In general, all the '05 R parts fit perfectly on the '04 X. After riding the two back-to-back, I'd have to say that the results are the same with the two conversions; both haul the mail . My buddy weighs in at around 200 lb. There is a sand hill (to the right in the background) that he used to blast in 3rd, and have to downshift to 2nd about 2/3's of the way up. Now, with the CCC, he can blast it in 3rd accelerating the whole way. For the record, we don't do a lot of slow, tight, 1st gear trail crawling. Others have noted a loss of bottom end, but most of our riding is in fairly open areas and we haven't noticed any downside. For both of us, the CCC setup has only been positive.