In Chicago, only WCIU (Independent) & WTTW (PBS) have made the best use for their subchannels. WCIU used to have FBT (brokered ethnic programming), but they replaced it with U Too, which is an extension of the programming on WCIU The U on 26.2 (also on WWME-CA analog 23) , MeTV on 26.3 (also available on WWME-LD 23.1) & that used to be comedy only, but since going nationwide, it's comedy & drama from CBS & 20th Century Fox libraries. MeToo on 26.4 (also available on WMEU-CA analog 48) & used to be drama only, but now is the local MeTV, & that includes the Sony library. Lastly, they have This TV on 26.5. Both MeTV & This TV are run by WCIU's parent company Weigel Broadcasting, & MGM markets both channels. For WTTW, since they have lots of programming that can't fit into their regular schedule on WTTW 11.1 (HD), they created WTTW Prime 2 years ago to show all the programming that would be considered primetime programming, & have a 24 hour primetime channel. That's on 11.2, & I watch that more than 11.1. 11.3 has Create, & 11.4 is V-Me (while not owned by PBS, it's basically PBS en español).
To go even further, here's other stations that have or don't have subchannels:
WGN-TV 9.1 (CW) - 9.2 Antenna TV
WYCC 20.1 (PBS) (HD) - 20.2 SD simulcast of WYCC - 20.3 Mhz Worldview
WCPX 38.1 (Ion) (HD) - 38.2 Qubo - 38.3 Ion Life
WSNS 44.1 (Telemundo) (HD, except for local news & non HD programming) - 44.2 Inmigrante TV
WPWR-TV 50.1 (MNT) (HD) No subchannels that I know of, but they have bandwidth set aside for mobile TV
WXFT 60.1 (Telefutura) (HD) - 60.2 SD simulcast of WXFT
WJYS 62.1 (Independent) (infomercials & brokered religious programming) - 62.2 simulcast of WEDE-CA analog 34 - 62.4 same programming as 62.1, but in different time slots.
WGBO-DT 66.1 (Univision) no subchannels
I did not include WWTO due to that station barely covering the western suburbs (unless they increased their power to 80kw recently)the low power stations that mainly air foreign language programming for the spanish, chinese, korean, & polish speaking viewers. You can go to rabbitears.info to see the entire list of stations that have or don't have subchannels. Note not all of the stations cover the entire market (that even includes the low power stations & suburban signal full power stations).