I've just started using one (yesterday). Unfortunately I've had to go with the smallest one as I'm at 99% power which means I'm often taking hits while waiting for it to finish. I have my first two Fire Groups with all my weapons (with cannon in FG 1 and missiles in FG 2), then one with just Adv Disc Scanner in FG 3, heat sinks in FG 4 and lastly the KWS in FG 5 (plus lasers as primary fire). I just switch FG afterwards (either immediately if being fired upon, or if not, after I've checked the info in the side panel that it's necessary). Netted quite a bit of extra creds.
You can't get around having to deploy your hardpoints. Having one with the longest range would be safer as well as quicker (as the target can be kept within the scan circle more easily). It's worth having a play with one to see if you like it.
I tried it in an Anarchy system at the NavPoint and USS points (plus any interdictions), but I imagine for most of the time in the future I'll use it at a non-Anarchy RES point, only scanning the Wanted ships. I seemed to make more at the RES points without the KWS than I did in the Anarchy system at the NavPoint, so for me it'll be used to sweeten the deal for some kills rather than an essential use-every-time piece of kit.