I have only been riding for about 6 months, I started out with a KLX250s and a harley XL1200N Nightster.
The Harley was fairly small (really small for a harley) but you felt the weight for sure, it was about 600 lbs.
The KLX250s is a great size and Super light weight, at about 280 wet.
I found that I gained confidence on the KLX really easily and learned alot on it.
The harley just wasnt the riding experience I was after, so I traded it in on a DL650.
I thought the same thing when I sat on it, holy crap the front of this thing is huge!
Once you ride it for 10 minutes you dont even notice it anymore, you dont spend time riding it, staring down at that front end, you just dont notice it.
As far as being a good beginner bike? Thats very tough to call.
Its going to be alot of bike for you to handle at first, yes you are going to feel the weight when going slow. But overall I find it a very easy bike to ride and a dream on the twisty back roads.
If you really take your time, and ease into it, you will get used to it as your first bike, but you might be a bit intimidated by it for a while.
You may want to look around craigslist, etc. and find some little dirt cheap Ninja, or dual sport of some kind, just to ride for a few months, get the fundamentals down.
Its ALOT easier to get yourself out of trouble and manhandle the smaller lighter bikes.
In the end, you will NOT regret the DL650 once you get it, its a fantastic bike in so many ways, I am VERY pleased.