This is our first year with WP and it's been great for us. I have a 2nd grader, 4th grader, and 5th grader.
We used Sonlight for 2 years. It was o.k. Some of the books we loved while there were others we barely made it through. I felt like we did soooo much reading but I wanted my kids to spend some time experiencing what we were learning. I did add in some hands on activities but I didn't like having to search out and order additional items. I also used their LA program and my kids didn't retain a lot of it.
I stumbled upon WinterPromise last summer and it has been a blessing for us.
We are using AS2 and really enjoying it. I added in the Middler Pack for the 5th grader. The read alouds have been hard to put down. I've only had complaints about one of the readers so far. I like that there are so many options for activities but I can pick and choose the ones that are a good fit for us. I also like the pace. I don't feel rushed if we get off on a tangent somewhere and I like that I can shuffle things around if I need to.
We're in WWII so in our reading today for example, we learned all about the goods America produced for the war. We learned about how families and individuals were leaving rural areas for cities. We watched a video online about the bombing of Pearl Harbor. Then 2 of my boys played an online game finding "Top Secret Files" and answering the questions held inside in order to keep the Ninja Headquarters from re-writing history about WWII. The kids had a great time and got to experience the time period in a variety of forms.
As for the bad, I'm not crazy about the LA. I prefer it to Sonlight but we will be doing other things for LA next year. Items are often backordered so you may receive your package in 2 or more shipments. And lastly, you should preview the IG a week or two in advance because things don't always line up. Last week we were supposed to listen to FDR's speech to Congress about the bombing of Pearl Harbor but we weren't actually reading about that until this week.
I don't know if that helps you in any way but that's been our experience.