I do them all except French (it's a common combination!) and I'm currently in Year 12, so don't have masses of experience so far.
Maths is my
easiest subject, although we've only done C1 and a bit of M1. Core 1 is really easy (especially since you'll be doing further maths, I assume you'll find it a breeze), if you're doing AQA further maths this year you basically learn it all in there apart from integration which is new, but that's easy so you'll be fine. Mechanics is okay at the moment, and is that compulsory with the new spec? I'm not sure what it's like at all to be honest. We haven't made much progress with mechanics at all yet, so I can't make much comment. suvat equations are relatively straightforward, although you do have to learn them. The only other thing we've covered so far is momentum, which in effect is really basic physics.
Further Maths is my
most enjoyable subject, we've done D1 and are currently about halfway through FP1. Decision maths is odd, you don't really feel like it's maths but you don't complain because it's easy
The only thing me and my classmates struggle with is timing in exams, however that can easily be improved over time. Further Pure is the "real" further maths content. We're about halfway through it now, and although complex numbers were a bit tricky to get to grips with at first, they're manageable and everything we've learnt since then has been fine. I think the FP stuff is really interesting, and it's what makes FM my favourite subject. It's definitely more advanced than regular maths, but so far not by much (this will most definitely change next year though). It sometimes can make regular maths seem a bit dull in comparison, but it's nothing too extreme as it'll also make it feel easier, allowing you to achieve top marks in it.
Physics is by far my
most interesting subject. It's also by far my
most difficult. I think the main reason for this though is because it is my only subject that's already new spec. So far we've done particles and radiation and waves, we're about to start electricity and mechanics. Particles and radiation is the easier topic out of the two, and also very interesting. It introduces a lot of new concepts that you won't have come across before, so it can be quite a lot to get your head around at first. Once you do though, it's not bad at all. Waves is in comparison an incredibly dull topic, and one that I've struggled with quite a bit. It's quite a big chapter, and it seems to jump around a bit in the sense that not everything seems to link nicely, it's simply bound by the fact that it's all got something to do with waves. It's a lot to learn, definitely. The main difficulty with physics though isn't the actual content but the exam questions. I just sat my physics mock this week which was made up entirely of specimen questions and they're really tough. The mark schemes are really particular with what qualifies for marks and what doesn't, so you really need to know the content well and do plenty of prep in advance to be able to nail the questions.
Unfortunately I know nothing about French, so you'll have to ask someone else about that. However I hope I helped with the other three! Any questions feel free to ask