Operator is proving to be really really useful, it appears simple but has great depth.
I absolutely love Collision, it`s unconventional though, but it is great for metallic and feedback based textures, which is something I am very much into.
Analog seems really good so far, although I`m not sure the oscillators hold up that well down real low. But I`m still playing with it and working it out.

I think as an all in one package it should fullfill pretty much all your needs, maybe more so if you are more doing this as a hobbyist.

I`m finding more and more depth with the ableton synths, I`m not convinced yet of abletons analog styled stuff (both their synths and the saturation/tube effects), but I haven`t had the analog synth that long so I¬m still playing.
Electric and Tension do their specific tasks very well, but again I`ve not fully dove into them yet.
And Sampler is fantastic, but ableton are masters of audio manipulation, so it shouldbe expected.

As for performance issues, I have had none with 8, both on the studio workstation and on my laptop. I`ve gigged with version 8 and had zero problems.