Looks like 3rd extensive facelift. So same powertrains. But it is not like ES powertrains are mindblowing either. I think the most important change this IS will bring is the interior (that I like but many find outdated). Yes, no high-performance engines, but compared to the common, 4 cylinder A4/C Class/3 Series, what do those have more/better?
M.P.G.
While we all sit here and want more power, the current IS engines are shamefully inefficient compared to the competition and it's something real shoppers do/will care about. It's nice that we're in an environment right now where oil is $30/barrel and premium is $2.40/gallon, but its extremely unlikely that prices will stay that low for much longer.
I'm not sure how you really compare the IS to the competition. When you look at price, performance and options:
IS 300 = A4 40 TFSI, 2 Series, A class, G70 2.0T
IS 350 = 330i, A4 45 TFSI, Mercedes C300, G70 2.0T, TLX 2.0T
The IS 350 no longer competes with the G70 3.3T, 340i, S4 or C43, TLX Type S, IMO, unless you're looking only at cylinder count.
... and this doesn't take into account the hack job IS 300 AWD with a 260hp GR V6 and 6AT with 18/24MPG. The 330i xDrive returns 25/34, the C300 4matic does 23/33 and the A4 45 TFSI quattro does 24/32.