People play games for the Hardware they have. You dont expect people to play Crysis 3 on Tablets do you ?? But if you have a faster GPU you will play more 3D games with higher IQ characteristics. And here comes Temash, you will be able to play more games or with higher Image Quality than BayTrail.
From AT preview, its clear that BayTrail has half the Performance of HD3000 at 15W in real Games. That is, it will almost have the performance of HD2000 at 15W.
3D Mark 2013 (IceStorm) must be the best case in GPU performance for Baytrail. I believe the driver is 3D Mark optimized. BayTrail scores 13850 in IceStorm, when two year old
AMD Z-60 scores close to 12000. Im expecting Temash to be close to ~20000 in the same Benchmark.
In real games, that drivers play more important role in performance, im expecting a 3.9W A4-1200 Temash to be on average close to ~70-80% faster than BayTrail Z3770.
Ahh and thats for DX-9, i dont believe BayTrail can even run DX-11 games(drivers).