I’ve had this quick-release bike rack for about 6 years with on and off use (no pun intended). I use it with two pannier bags to commute to work carrying my laptop on one side and a set of clothes on the other. I like being able to quickly take the rack off of my bike for recreational riding after work or on the weekends.
It’s very easy to install/remove and requires no tools. It does exactly what it’s supposed to and I’ve been very happy with it. It is also one of the few racks that can be used on bikes with rear suspensions. I bought mine at REI for about $60, but you can find them at Amazon. There’s also a model without the vertical pannier supports, but I think the limited functionality is not worth a $15 savings.
My seat post space was at a premium due to a bike light and an under-the-seat bag, so I attached a wooden dowel rod vertically to the back of the rack with a single screw to create another “seat post” for my bike light. The last benefit is that the rack acts as a mud/splatter guard for your rear wheel should you ride to work on wet streets.