If you’re running AES-128 I would expect the performance will not be fantastic, the thing is only a 400Mhz processor after all…
I have been meaning to do some throughput testing on my Mifi for our own purposes, so I’ll try and do them in the next day or two and post up results. I expect the CPU will be the general limiting factor especially if you’re asking it to do encryption ontop of regular NAT work…