Hi Alan,
I bought my first BMW - an 1150Adv from SPC 18 months ago. I was a commited 'sportsbike' fan for 27yrs, and had a 'bird at the time. I had a go on one out of sheer curiosity and wasn't convinced after 90 minutes playtime. I handed it back and thought " Just doesn't quite do it for me".
8 months later I was back for another go.
This time it was the 'bird I dumped and the GSA that took me home.
As a 'first bike' ?
I'd say no.
Why ?
Its a LOT of bike, not in the same way as a Gixxer K6 or a Blade, but its formidable none the less.
I have done a lot of riding in 27 yrs and more training than you can shake a stick at, but despite this I still found the transition from a 'normal' sized bike to this behemoth fairly challenging. Even 6 months on it was still a big bike physically and requires a good sense of balance at U turn speeds if you don't fancy back strain or scuffed engine bars.
Do an E-Stop on this and not be in perfect control and you WILL be eating tarmac.
I guess you have 'road sense' from car driving ? which is a help for anyone new to 2 wheels, but its no substitute for bike miles and how they react when you either make an error or have to react to someone else's.
I'd say do 12 months on something which does'nt intimidate you - and if the GS doesn't then I'd be mildly surprised - then see how you feel on one.
If its a bit of a step up for you will know, and if your head tells you so then LISTEN !
Don't struggle with something you are'nt confident and comfortable on - 2 wheels is NOT the environment in which to take leaps of faith.
That said...they are IMHO the best bike I have had the pleasure of owning.
Ride Safe and good luck.