FWIW, I just noted they raised (albeit only slightly) the points required for Marriott Gift certs so one needs 40 more points (less than one days quick visit) for a $20 cert at 2190pts.

There are now 4 Marriott choices instead of just two.
$10-1100pts
$20-2190
$25-2675
$50-5350

American Air $50 certs are also 5350pts.

CDnow certs, as I think PG once noted, are probably the most "valuable" (depending upon how you value items) since:
$5- 500pts
$10-1000
$20-2000

It does seem in general that it may well be best to cash in with most of these programs on a fairly routine basis, since changes are rarely if ever announced in advance- and even less likely to be beneficial.