We just tried Zum a week or two ago. We ordered the day before for a ride at noon, were told it was all set. My husband checked the app in the morning and it said there was no driver (they didn't actively attempt to notify us of this). We cancelled the request and rearranged work schedules so we could shuttle him at noon that day. That was our only experience.
We have had good experiences with Zum. Not sure what your exact needs are but the drivers we had all used SUVs and they were easy to schedule and reliable.
We have used Zum on multiple occasions. They have been reliable. They've always had a driver available when I needed one and you know the cost up front. I tried another service once and they didn't have a driver available. I didn't know that they didn't have a driver, though, until 24 hours before, so I was scrambling last minute. Not what you want as a busy parent. Zum doesn't match you with your driver until 24 hours before, but they have always had a driver for me. So I don't worry about that. I think they have an option to set up recurring rides if you have a regular activity.
A good Shuddle replacement is Zum (http://ridezum.com), which offers rides & care in the Bay Area for kids aged 5 & up. I've used them for my 11-year-old with no issues. Search on FB or Twitter for promo codes that give $20 ride credit for new users. Many Shuddle families & drivers have started using Zum after Shuddle closed -- good for camp/school/activity transportation.