Sts,
I have put a lot of time in on a N model and I have not seen any significant problems.
Every pilot complains about the power of any airplane and they replaced the 320 with 360.
The Lycoming is a bit cheaper on the annual (4 cylinders) compared to the continental (6 cylinders).
It adds power and speed.
I have a lot of hours in continental powered 172's and actually preferred them over the O320.
Look more at the improvements the models give and read the logs very carefully.
A honest pre-flight inspection by a mechanic who has not touched that 172 is worth every penny.
This means in reality have the mechanic perform an annual. Expensive, but they will find things that will cost you in the long run.
Because they are not risking their license, they will blow the whistle on less than great repairs, over driven rivets, etc.
They will also check to see that every single piece has been upgraded..... Instead of the same old mechanic who "knows" it is done.
I have found magneto's that are not assembled correctly, 50 cent capacitors that are reused.
In one engine, a FAA required bolt replacement was reused. etc.
Ragwing