If a host is not delivering super service.  Leave them.  Right away.

Slow service can reduce visitor interest in your website.

That will tank your sales.

Slow service can compromise spidering.

That can cause ranking problems.

Don't work your ass off on your website and tolerate this type of service.

If it costs a few bucks more per month so what... look what you are losing.

A host that has lots of important websites as their customers.  Websites that will move if they are not getting fantastic delivery.

Just sayin'....

Some hosts who offer unlimited bandwidth and unlimited other stuff often find ways to throttle your success by limiting your number of database connections, users online or some other BS metric.

Not sayin' that is what is happening to you here but sayin' that I learned my lesson to host my websites where they are going to charge me for all of the resources that I use.  That way they win when I succeed and not they become defensive when I succeed.

Call 'em up and ask them what's going on?  Bug them.  Tell them that you want a reason why it is so slow.

You work hard to make your site a success.  Don't settle for poor hosting.

The way that search engines have treated subdomains has changed repeatedly over time.  The way that they treat a folder has been much more consistent.

Also, in that video did Matt Cutts specifically state that if you divide your site between a subdomain and a root domain will the power of your site be the same as if they were united?

There are a lot of domains on the web that have many subdomains that are owned by various people.  The ranking power of subdomain A does not influence the ranking of subdomain B on these sites.

I think what EGOL means is that switching the domain to your hosting provider means you loose control of certain things within that domain which can be very important to seo. What could be a good compromise here is that you look at putting the shopping cart within a folder on the domain...

That is it.  Some shopping systems require you to place all of your content into their system - your articles, your homepage, everything.

Then they can charge you high fees on all of your bandwidth, limit your ability to install software such as wordpress, use htaccess, have full and complete control over the format of your pages, have formats that require a lot more time to manage, not allow you to run scripts in the cgi-bin, not allow chron jobs.

They all do not have all of these problems.  But some are really limiting and I would not want to marry into something that will limit my options.

I would look for a very flexible cart that allows you to have full control over the entire domain.  Confining cart activities in a single folder would not be bad, but I still think that is limiting because I would like to have the ability to place "buy buttons" on any page anywhere within the site - even on pdfs if I want them there.

Lots of people come to these forums saying that they can't do one thing or another because of their shopping cart.

I have read arguments that putting your cart within a sub domain is not a good idea because any clout of the pre-existing domain will not be shared with the  sub domain; that they will be treated as two separate sites.

I agree with this.  All of my sites are done this way.

I have also read that using a sub domain is a good idea being that the content focus of the main domain (marketing and blogs) is different form the focus of the sub domain (product sales), and that the two components would benefit form earning their own rankings undiluted by the other.

This is BS from an SEO viewpoint.  Although some snooty marketing people might recommend it.

You can have unique banners for the store and promote it in tasteful ways that make this distinction for your  visitors.

It's not about how it is hosted (subdomain vs folders)... it's how your navigation presents it to visitors and search engines.

And, I have also read that search engines are getting good at being able to deduce that an eCommerce sub domain is legitimate extension of a content intensive main domain, and that they treat the two components as a combined whole.

Where are you reading this stuff?

Have the cart as a sub domain of my main site, or move my existing domain name to be hosted by the cart provider...

The day that my sites get hosted by a shopping cart provider is a day that you can bet big money that I am dead and under.

I want my pages to be finely crafted arrows.  I don't know if I am going to get that from a shopping cart system.

Someday you will probably decide to leave that shopping cart provider... it will be a lot easier to make that decision if you are not completely married to them.