you could still try 300 it has the advantage of being more fine grained than 100 and a lot less overhead than 1000.
It makes a difference when you're working on an audio project that has 50 tracks going at the same time. On 1000hz I can get my latency down further than I could on 300. I can mix on 300 but not record. I also haven't seen that much of a negative impact considering I mostly just use my system for browsing and writing papers when I'm not doing audio work.
context switch overhead. Reduced IO performance. A lot of other stuff.
Look at my other benchmarks above, especially on the RT kernel which is essentially an extreme version of cranking up the HZ - albeit a really useful one. Basically the tradeoff is that you get a much more responsive system at the cost of throughput. For my specific case it's worthwhile but I'd imagine for 99% of desktop users voluntary preemption and 300 works great. I can't really tell the difference on a server kernel with no preemption at 100hz on a good multicore processor anyway.