Business-oriented Hotel Antupirén (Freire 186, tel. 065/350561, reservas [at] hotelantupiren [dot] cl, US$56/67 s/d) has attentive, efficient service and a good buffet breakfast. Some smaller, slightly cheaper rooms are lesser values.
Hotel O’Grimm (Gallardo 211, tel. 065/ 252845, fax 258600, www.ogrimm.com [1], US$65/76 s/d) has attentive service and large rooms with all modern conveniences. Its attractive bar also has a basement pub with occasional live music, but it’s acoustically insulated.
The contemporary Hotel Le Mirage (Rancagua 350, tel. 065/255125, fax 065/256302, hlemirage [at] telsur [dot] cl, US$55/78 s/d) often fills with groups; rates include private bath, cable TV, and most other conveniences, but it’s well-worn for its age.
The business-oriented 
Hotel Gran Pacífico (Urmeneta 719, tel. 065/482100, fax 065/482110, www.hotelgranpacifico.cl [2], US$78/90 s/d) has spacious, comfortable, and immaculate rooms that are also soundproofed; those facing southeast have the best views. Amenities include a gym and sauna.
Up the hill from downtown, the new Hotel Diego de Almagro (Ejército 516, tel./fax 065/320300, puertomontt [at] diegodealmagrohoteles [dot] cl, US$88/98 s/d) is promising but suffered a surprising shortage of staff in its earliest days, affecting the quality of service. If that gets straightened out, it’s as good or better than the Gran Pacífico.
Links:
[1] http://www.ogrimm.com
[2] http://www.hotelgranpacifico.cl