It's absolutely worth it to me. I stayed at Hojo in Jan for the $59/night rate, and we were upgraded to a premium Disney view room. The staff was super nice and the hotel was fine. The price was amazing.
However, it lacks all of the magic for me. I hated the walk on Harbor--not because of the distance, but because I hate walking on that busy, ugly street. When we returned to our room the first night, we had to step over a homeless guy on the sidewalk near the hotel, where it was very dark and no other pedestrians were around. It was a big mass of bushes (with plenty of room for lurkers), the sidewalk, and the street. If you stay offsite, don't walk back to your hotel at night on the Disneyland side unless there are others with you!
The hotels I've stayed in offsite (with the exception of the Hilton) were basically standard motel-type properties as far as the in-room amenities. It may sound petty but I LIKE granite counters and wood furniture and real glassware. I love the Disney touches everywhere in the rooms. I love having a place where my kids can watch the old Disney cartoons while we're waiting to be seated at the restaurant, where there is a ton of memorabilia to look over, where characters stroll through the lobby and grounds. I love the fabulous landscaping and pools.
I also love DTD, and not because I'm shopping but because I enjoy seeing people having a good time. I like the musicians playing and love watching kids dance to the music. I love all the fountains and decorations. It's much nicer to me to walk through that than down Harbor.
There are a lot of benefits to staying onsite, as previous posters have listed, but to me the biggest benefit is the sense of always being in the resort, or to be more exact, of NOT being in the somewhat ugly reality just outside the gates.
