I play Osu! with a tablet since I joined, so I can't play with a mouse one bit...I wish I was able to, though...^^ When I first started, I played with tablet only.
Standard: I use a tablet. A big one by Trust whose model number I forgot. I didn't go for it because it felt easier than using a mouse (couldn't do anything higher than Normal diff with it), I chose my tablet simply because it enhances the experience for me. I feel like I'm actually giving my input on the song as if I held an actual instrument on my arm, and I love it!