Give the program a facelift.
As I've been looking around for a new way to lesson plan I've been comparing and trying out different programs. One lesson planning program I almost went with is Planboard as they have a very contemporary, aesthetically pleasing program. After comparing the Planboard program and yours, Planbook wins hands down as far as being more feature-packed, especially in terms of lesson sharing abilities, but the overall feel of Planbook looks like something designed in the 90's. The features you're putting into the program are great, and I plan to stick with Planbook, but a facelift into the overall look and feel of the program would be a big plus.

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MW commented
I actually LOVE how basic it looks. Features are way more important to me than looking "contemporary." I've been able to customize mine enough that it doesn't look so basic.