I think the best tote you could buy would be a Tutto - I have the Tutto Office-on-Wheels and one trip through a trade show was enough to convince me. I never struggled with that bag, no matter how full and heavy it was. My luggage, yes, but the Tutto was effortless. In fact, in airports, I would stack everything else on top of the Tutto and breeze through.
If I needed a tote for a sewing machine, I don't think I'd settle for anything less - it's that much better than anything else out there.
It's very stable so it doesn't tip over no matter how tight a corner you're turning. You can pull it up up and down stairs without any trouble at all.
It has a very sturdy frame, so you could use it to sit on if you're in a crowded place that lacks chairs. (quilt shows, trade shows, etc) It has a U-shaped stiff handle, so you can steer it away from you or toward you.
The compartments are very handy and so is the access from the top and sides.
I probably sound like a salesman, but honestly, the thing really is all that. :)