Is reloading bullpups hard/weird/difficult?
No. Even when I first started using them, it felt so natural. I'd used 'normal' configurations quite a bit before, so it wasn't like the L85 was the first firearm I'd ever handled or slammed a magazine into.
Is it difficult/weird to reload at certain times? Well, like all firearms, yeah, it can be a bit of a juggling and balancing act to reload if you're hugging the ground, wearing a rifle sling and lots of webbing.
Linking into what Dave said, its more down to personal preference than the actual guns. I've always found reloading a 'normal' gun like an Armalite weird.
Rain?
Brilliant. Love it. It creates a brilliant atmosphere.
If you have that light drizzle with a light mist and you're playing in woodland, suddenly you feel like you're in a Vietnam war film...