Firstly, every Elise is a very different car, I test drove about 20 before I found one I really liked, and depending upon how they've been looked after and setup, they can vary wildly.
My Elise is an old one and feels a lot more raw than the latest I've driven which is an S2 Exige S.
I find GT 5 Prologue in professional with all aids off, a little more HP and a little less weight to be pretty close to the performance of my S1 Elise, the old GT's had too much body roll compared to even the stock Elise, but I felt that was exagerated in game to give better feedback without the G's being applied to the driver.
I think as I said in some other thread, that the tyre traction is either right from an acceleration decelleration point of view on one tyre, or from a lateral grip point of view on another tyre, but this cannot be adjusted to get a correct match in GT5 Prologue with the tuning available.
The biggest area where the simulation is wrong is the time between gear changes, there is no way I can get my car into the next gear that quick, and have compared side by side video footage of 0-100 out of curiosity.
I've only driven two on the track at my limits, my own, and an old Exige, which felt similar to how mine feels now with the suspension and tyre upgrade. Also, I've only driven my own in a ghymkana situation, this is where you really notice the Elise's understeer, and in the wet, you can go from understeer to oversteer a lot quicker than any other situation, but, similar to a handbrake turn, when you get it right, it is the best feeling ever!
I've not had too much trouble with the A048's, although they pretty much get used for weekend mountain drives the majority of the time. To be honest they perform better in the wet than I expected and way better than the old Road Yoko's I used to drive on. (Sorry the specific part number escapes me).
Overall GT can exhibit some of the twitchiness and interesting MR behaviour you get on the edge better than any PC Sim I've tried.
For example when braking hard, you can lock up and get the rear trying to overtake the front wheels and this to me feels very realistic now.
Also, if you lift off mid corner whilst on the edge, the rear will again break free and try to overtake the front wheels, which is what I was describing earlier.
Not many Sim's or other games get this right, so I believe GT is currently modelling my car better than anything else I've tried.
I find a lot of PC sim's over exagerate all the grip characteristics and model this behaviour but much more soon than GT does, and I find GT to match better with my experience of driving the Elise.
The other thing that GT gets right is the turn in (or lack of) on the edge, which when you back off a little the nose comes in at the start of a corner, to me this is what they really nailed, and what gives me the most authentic car feel, you can feel the weight transfer back to those front steering wheels, increasing traction and then turning the car.
Here's a pic of my home made cockpit, I turned the pedals upside down, and swapped clutch and accelerator to get a better feel, all the dimensions are pretty much identical to that in my elise, except the wheel is smaller and the travel of the gear lever is smaller. I use an office chair with the base removed, which as you are probably well aware has a little more padding than the Elise seat

.
Also a pic of my Elise compared to the one I setup in GT4... I used the GT4 different wheel options to help choose new wheels when I swapped to A048's and chose the rimspeed 12's... Geary at Elise Parts got them powder coated black... to be honest the only reason I did that was to make it look more like the ones in GT...
I can't wait for GT5 Photo mode!