At least on the (carbon-brake equipped ones that I've flown) 140/145 and the 170/175, reverse thrust is only really used (above idle or at all) if the runway is wet or contaminated. Autobrakes low and idle reverse doesn't do much on this jet. Above those settings, though, the effect is...well, it's there.
Yeeeeeeeeep. I know the performance data SAYS that I *can* land Flaps 5 and not use TRs at all in Santa Ana, but that doesn't mean I do it; it seems much more prudent to land FULL and use reverse until a safe stop is assured. Double ditto for Burbank. I don't want to have to explain why I didn't use all available resources to stop given the relatively short length of these runways, performance data notwithstanding.
If you THINK you need to use thrust reversers, put them out there, and put them out there early, and spool them up early. Engines can take just this side of forever to go from ground idle to a usable level of reverse, not to mention the possible delays in just getting the sleeves or buckets in the reverse position.