I have! Well, weve got both actually. People do actually look at the 172. Ive caught people peeking in through the windows of both cars quite recently!
As far as drivability and fun goes, be prepared for a bit of a shock with the handling. When you first get out of a Williams and into a 172, you will find that someone has stolen your turn in
. You might also find that the 172 rolls too much (a 30mm drop will take care of this completely) and you have to commit to a corner before you go into it. No more sneaky last second adjustments mid-corner like in the Williams. Not unless you especially like travelling backwards, anyway! The chassis and general feel of the car is fine, I just think that excessively high ride height and soft springs lets it down a bit.
However, having said that, Ive just spent a weekend driving in North Wales with the 172 and have had a great time. Once you get the hang of the 172s handling (and accept that it isnt the Williams!) you will find that its a very rewarding experience. It really flows through B-roads. I gave a Porchse Boxster a tricky time keeping up with me at one point (looked in the rear view mirror to see him getting out of sorts on a corner that Id just blasted though!).
In many ways the softer, higher suspension works for the car, and you can really dig in to corners, its just that initial turn in and adjustability that is missing from it at the moment.
Anyway, thats only half the story....the engine is an absolute gem. So much fun to drive at low and high revs. Its got a lovely light clutch too compared to the one on the Willy/Valver. Overtaking manouvres that required some sizing up in the Williams can be dispatched "point and squirt" style in the 172. Its just got so much go up in the high revs. In fact, getting back into the Williams, I keep smacking into the rev limiter at 6.5k as Im wanting it to go all the way to 7250!
All in all, Id recommend keeping both cars if you can afford to. The Williams is definitely a future classic (as will the original MK1 172s be, I think, with the alloy bonnet etc.) and deserves to be polished and only taken out at the weekend. The 172 makes a brilliant day to day car (its sooooo much quieter inside!) and a seriously good b-road car.
If you want any more info, feel free to PM me (I also had a MK2 172 as well, if thats what youre after getting).
Rhys