I also use MTT and love the client feature. I provide SLT input for several schools and can share (with permission from parents) the notes for all the children I’m working with in a school with the INCO. Not only does this mean that I can share personal information securely with the school, such as reports/progress updates, but often they are able to find the information they need about my input (eg when I saw the child, what the current targets are, copies of the last report) without having to ask or wait for me to get back to them – this saves us both time so they love it too. I also attach resources to the client record so if school staff or parents mislay materials, they can just print out another copy straight away. I share the record with the parents too.
By the way, MTT has the full range of IPA symbols for writing notes, a diary/booking system and invoicing too.
I know it costs more than other options but, for me, I get what I pay for: peace of mind around data protection and time saved while supporting collaboration with parents and especially schools.