Okay, bought this one, got attacked by my Mackie Blackjack drivers again so something had to be done.
So, some observations about Tascam 2x2 for posterity (and future google searches): so far it seems good indeed. Installed (W7/x64) and updated the firmware with no problems. Latency's okay - reported 1.4/8.7ms at 64 samples buffer, 2.9/10ms at 128, 5.8/15ms at 256. Values seem about right (if oddly asymmetrical), as loopback test shows automatic latency correction being off by mere ~26 samples(0,5ms) at 64 buffer, which is decent I guess. Latencies are a bit worse than with Blackjack (it was below 8ms rtl at 64 samples and below 13ms at 128, pretty nice actually).
So far it works nicely, plays windows sounds, did a bit of guitar noodling over a relatively(for me) complex
project with Slate drums, couple of POD farms, waves GTR, guitar freebies and a bunch of synths and effects - looks like it's doable to track stuff at 64 there. Guitar input has some spare headroom, altough gain knob past 9 o'clock makes it clip with my, according to pickup manufacturer, "mid-to-high" output guitar.
Things I don't like - driver is not multiclient (ASIO mutes any other sound in the system) and headphone out is pretty quiet. But I can accept that if that thing is safer for my ears than Mackie blackjack.
Will update if turns out I hate this thing.