Zedder,
The timing for this discussion couldn't be better for me. When my wife and I bought our current home 6 years ago I thought that moving from a 1 car detached to a 3 1/2 attached would be all I ever needed.
Then we started accumulating lawn tractors, snowblowers, tillers, etc... Now my garage floor looks more like a collection point for leaves, grass and dirt than a quality garage/workshop.
This morning the excavator showed up and started digging for our new 30'x40.5' workshop. The new deal will give my wife and kids the current garage for everything that collects dirt and the new facility for the collectibles. Yes, Listening to alot of you guys has inspired us to build it with 10' inside walls so we can accommodate a lift.
We live in one of those "deed restricted" (anal retentive) subdivisions, so the planning,lobbying and approvals have taken about 8 months to get wrapped up. But, I'm sure it will all be worth while in the end.
Build it is large as you can tastefully can and you will be in good shape. Adding hydronic heat in the floor may also be a plus since you're blessed with fine northern weather like myself.
Good luck!
Blair