I have sport seats in my E92 and love them, but when I ordered my X1, I chose not to get them.
I tend to agree with kosmo that the sport seats are much better for the twisties and the regular seats are better for long distances, but the difference in highway comfort is minimal. Sport seats are still good on long distances.
Overall, I prefer the sport seats, but due to limitations in optioning, I did not get them this time. My preference would have been to get an M Sport, but I was concerned about the stiffer suspension on the bad roads where I live. I didn't want the Sport Line basically because I just can't stand either of the trim options (aluminum or black gloss). Had there been a wood option for the Sport Line, I certainly would have gotten it. Realizing that my usage wouldn't include a lot of sporty driving, I decided the regular seats would be fine for me.
If I were you, living in California, I would go for the M Sport and enjoy the much better handling characteristics, sport seat comfort, and IMO, better styling.
2013 X1 35 MB/Black/ULT/CW/HK/Lighting/Paddles
2009 335i xDrive Coupe Black/SB MT/SP/PP/CWP/PDC/Logic7/iPod
2004 325iT SB/Black SP/PP/CWP/PDC/HK/Step/Xenon
2006 X3 SG/Black PP/CWP/Xenon
2006 330i SG/Terra MT/SP/PP/HS/CA
2004 330i SG/Black MT/SP/PP/HS (my
2001 325i SG/Black MT/SP/PP/SF/Xenon