Maybe it’s an Asus problem (don’t know how this could be considering this is a Nexus) or it could be indeed Tagra’s fault. I had a Transformer TF101 which also got unbearably slow after a few months of use. My Nexus 7 is quite OK though for now, definitely slower and more frequent performance hiccups than my Nexus 4, but definitely usable and usually nowhere near what I’d call slow. But that was also the case with the Transformer in the beginning, so maybe it might slow down in the future.