Funny you are talking about GPSs, I just replaced mine today. I always prefer to use the suction cup directly on the windshield. I place the GPS just Under the rear view Mirror. It block the line of sight a little but I never found it to be a problem. I have a 5" model, if I was using 7" I don't think that would work though.
Anyway, got the Garmin 2595LMT as a replacement for the Tom Tom Via 1535M that I purchased 3 years ago.
I use my GPS a lot, my main job is doing deliveries and GPS can save you a lot of time and pain in a city like Montréal. Streets seems to have been designed by a bunch of monkeys searching for bananas. One ways everywhere, some of them spliting in both directions, some Streets have ones ways meeting each other, it's a mess. So thank god for the GPS system
BTW, as a side note. For comparisson, I think Tom Tom's software is a bit nicer. I feel it was easier to follow directions on screen on the Tom Tom and the voice guidance was a lot more natural.
Garmin have much better maps, I will have to work with it for a while to see if it is true but the Tom Tom would try to make you do illegal things from time to time, and they are really bad at keeping maps up to date. On that note my Tom Tom was supposed to get lifetime maps but I was never able to get them. I sent several emails to Tom Tom and never got an answer... I strongly recommand people stay away from that company.
The new Garmin also comes with lifetime maps, I really hope I won't have the same issue.