I'm going to get a thumbs down for this, but honestly I would use the email address your ISP provides. The reason I'm saying this is because 1.) You pay for their service so they have every pressure to fix something if it doesn't work, 2.) This correlates to number 1, but you're basing it on an official ISP which is giving you access to an email address, unlike something like Google which you signed up for for free.
All of what I just said really is not strong enough to warrant NOT going with something like Gmail, my gut level just tells me to stick with what your ISP provides. It's just a logical thing - if you pay per month, you can put that much more pressure on them to fix any problem. With Gmail, I don't even know if they have a telephone help center, and #2, it's free so you can't logically bust their ear out with complaints as much as you could with Comcast (because at least you're paying $40 a month there).
And also a third, but unrelated reason, is that I like people seeing the ISP I use in my email address. I purposely take out my name off my email client so they just see the the actual email address. When I see a Gmail address come in I get a cheaper, less secure, more mass feeling than when an email with "Bellsouth" or "Comcast" comes in.
Again, I'm definitely going to get a thumbs down for this post, but I just wanted to say my opinion.