I have Suzuki grips on my Wee (bought secondhand of ebay) but they are actually the type fitted to the Glee onwards with the"smart" push button controller as opposed to the earlier rotary type and are described as 180 deg, only heating the lower part of the grip where your fingers are and yes as others have reported not a lot of heat.
I have put up with the lacklustre performance but a few weeks ago while doing some maintenance that gave me acccess to the grips wiring and connectors I decided to do a little investigating.
Each grip is 5 ohms resistance and they are wired in series so 10 ohms and lets say running at 14 volts that's 1.4 amps/19.6 watts, Oxford grips are about 50 watts. that's why in my case at least they seem so poor.
However for me I have found a solution and I say now I take no responsability for anybody attemting similar, I have "overclocked" the OE grips.
Having a rotary controller left over from a set of faulty Honda grips I stripped off a mates bike a few years back I decided to do a few tests with the grips reconfigured in parallel.
We are now looking at 2.5 ohms and with 14v that's 5.6 amps/78.4watts which I suspect would literaly be "meltdown" within a few minutes but with the measured output limited to 4a/10v (40w) which equates to about 75% output on the controller they have plenty of heat even through winter gloves and to date the grips have proved durable enough to handle the increased amps and heat.
What I have not got around to yet is trying them back on the original controller.
Where as the rotary controller is easily modified (small self tapper screw etc) to restrict how far it is turned the button controller presents a problem, first press full power, but if my ohms law is still correct a 1 ohm power resistor added to the circuit would get the target 4a/10v/40w at the grips with controller on full.
Somebody check my maths please