:) Agree with Catherine. She has an amazing strong personality hidden behind her "royal" safety shell. If you also played Eternum (which you really should) Alex(andra) would be somewhat similar and is one of the reason she's usually under the top 3 (with Luna and Nova).
Some complain that Cosy Cafe doesn't really have much interaction. Though as a programmer and former game dev myself I even prefer the linear story. This lets the dev focus much more on the story. Harem Hotel in my opinion has overdone the "choices" you can make and as a result, bugs and plot errors are piling up as the development progresses which is kinda sad. AVNs with (too) many choices are almost required to play with an actual walk through guide, otherwise you miss important things. Too many optional branches also just increase the workload for the dev and reduces the actual content. So I'm 100% with Cosy's decision to make a linear plot.
To me an AVN lives between reading a book and watching a movie. It provides the best parts of both worlds :)
(ps: I said it already in another comment, specifically for Eternum, AVN now stands for Audio-Visual-Novel as it has literally 300+ music tracks. Just quickly checked, it's 231 + 29 + 51 == 311 a wopping 665MB in mp4 and ogg. Additionally it has 1014 sound effects)