You are right to ask these questions as you will be spending a lot of money.
You are also right to assume that there are an awluf lot of happy owners with no issues out there. If Renaults are as bad as some would have you believe there wouldnt be any on the road.
Every brand is not without its problems - even Toyota.
I know someone with a Verso diesel that has had no end of problems, engine has been out at least twice, gearbox etc,
leaks, he has it as a compnay car and cant wait for the lease to end! he wont have another one.
Renault have improved over the years and a lot of gremilins have been ironed out. The new Grande Scenic is the latest incarnation and has only been around for a few months, quality is said to be greatly improved and Renault did loads of testing before launch.
You will have the benefit of a warranty - which although hopefully you wont need it is always there for the first 3 yrs.
Try and get the Scenic for a decent test drive and try it out with kids,dogs , wheelchair etc - whatever you intend to use it for.
At the end of the day only you can decide - go with your gut instinct as these are usually the best ones to go with. Once you stop to think and ponder for too long over a decision about anything doubts begin to creep in.
We have had 3 Meganes in the past and one Laguna and also awaiting delivery of a 2010 Laguna SportTourer Initiale TomTom.