With regard to cpu usage and idle I was under the impression that sar and vmstat get their info from the same place, however please find some figures below all taken from the same system:

sar shows no idle and loads of system but vmstat shows plenty of idle
so why the difference, I tend to believe vmstat as the machine does not feel sluggish. top also shows all cpu's have plenty of idle but there are process within top showing 90-100% usage.

sar -u 1 5
Linux 2.6.9-42.0.2.ELhugemem (apps906-p.lvt.us.ml.com) 11/30/2007

11:34:42 AM CPU %user %nice %system %iowait %idle
11:34:43 AM all 7.53 0.00 92.47 0.00 0.00
11:34:44 AM all 3.23 0.00 96.77 0.00 0.00
11:34:45 AM all 1.12 1.12 97.75 0.00 0.00
11:34:46 AM all 2.38 0.00 97.62 0.00 0.00
11:34:47 AM all 1.98 0.00 98.02 0.00 0.00
Average: all 3.26 0.22 96.52 0.00 0.00

vmstat 1 5
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 0 6184392 342536 7616324 0 0 0 22 0 0 4 12 84 0
1 0 0 6184328 342536 7616324 0 0 0 0 1491 946 0 23 77 0
0 0 0 6184520 342536 7616324 0 0 0 0 1373 581 1 21 78 0
1 0 0 6184520 342536 7616324 0 0 0 0 1417 791 0 18 82 0
2 0 0 6184528 342536 7616324 0 0 0 856 1253 334 0 21 80 0