The early Megane II was prone to
failure, door pockets filling with water and problems with water getting into the fuse box. Most of these problems should have been ironed out during the warranty period. If you have the vehicle registration you can log onto this:
Renault : My Renault Login
This is on the Renault UK site and you will be able to check for any outstanding recalls.
This forum may help you decide as it is strictly Megane II's
The Mégane II Owners' Club :: Index
Personally, I find my Megane a pleasure to drive although only being a 1.4 it is a bit sluggish but goes well once you get the revs past 3,500rpm. I do have quite a tappet rattle from mine but the local dealer is not prepared to get in there and sort it until the performance/fuel consumption is adversely affected.
Take the vehicle for a test drive and listen for tappet rattle at 3,100rpm especially when decellerating. Brake squeal can also be a problem but not every car suffers from it.
Spend time looking through the Megane II owners site and see what is written in the 'ownership problems' category.