Pros
Worked here for 3.5 years and it was a great place to pick up a large variety of valuable tech skills. Working with a wide range of clients lets you get familiar with a huge range of hardware, software, business processes, etc. With so many clients with ever-changing needs, it is never boring. There will always be new projects with new technology happening and if you aren't already involved but want to be, all you have to do is ask. You don't have to struggle to get the tools you need to do the job here. This is not a business that hamstrings their employees by giving the employees the bare minimum laptop, supplies, etc.
Cons
The fast-paced environment of an MSP is not for everyone. Maintaining work/life balance can be difficult at times. There can be times when multiple projects coincide or outside circumstances create a spike in workload that needs to be handled.