If its using the latest Tegra technology but with a reduced number of gpu units it can match the earlier development kit performance in graphics with lower power requirements.
I don't think I'd have a gaming session beyond 5 hours ever so its perfect for me.
Remember the wii u development kit was 352 gflops for gpu but final retail was 176 gflops so there is normally some over-capacity in the development kit. I feel the retail version of Switch will be about 400 gflops docked perhaps 200-250 in portable mode. This would work perfectly with about 5-8hrs use.