We had a Joovy Caboose and it was a lot of fun. However there are some flaws. As Milk says the newborn has to go in a car seat. We had the Ultralight and the front recline was very good really but it compromises the child in the rear who then needs to slide the seat towards the parent and perch on the edge.
As Misdee has just found out - she had one delivered today - a child can easily reach the front wheels - we didn't have this issue with an older baby - the footrest lifts up for them. Plus there is direct poking, hair pulling, general annoyance access to either child as they are back to back if the rear child is seated.
I didn't find the basket access too bad - my eldest loved standing up and helping me. But I forgot she was barely strapped in and tipped up to go up a step and she practically flew off! The harness allows a lot of movement, so your eldest needs to be reasonably well behaved.
The Ultralight pushed like a trolley - like a B&Q trolley as opposed to a Tesco one - the ones you put planks of wood on. It wasn't bad to push ie not heavy - it just felt like a trolley not a pushchair. I dont know what the regular Caboose is like. The Ergo was plain horrible!! Looks great but unpushable. I have never listed a pushchair on Ebay so fast!!
Other downsides - the through hood. Thankfully we had ours in summer but I can't imagine the bitter wind howling through past the children's heads in winter. My two like being snuggly. Also its hard to fit any footmuffs on.
Its also surprisingly long folded.
This and this might help to see where the rear seat position goes etc.
I have to say my daughter adored the Joovy - she was desperate to hang onto it - but hubby made me choose between the Joovy and Peach Blossom - no contest! We loved the interaction between us - we used to talk loads and she loved the option to stand up or sit down. I could get my shopping home although the odd time DD was holding a bag on her knee as theres nowhere really to hang anything extra.