It shouldn't necessarily worry you, in the fact that they are a bad host or anything, but latency is a very big deal when it comes to hosting. CDNs can't cache dynamic content, so when you're dealing with a forum, this becomes a very big deal. What I find absolutely hilarious is that people install all sorts of plugins and caches and such to shave a few milliseconds off their page loadtimes, but then will go with a host that's halfway across the world. That's a stupid way of doing things. Any tiny loadtime you shaved off the site, is going to negated by the large latency.
On average, you're going to find 90-150ms latency from the UK to the east coast US. It's another 70ms or so from the east coast to the west coast. The midwest will be roughly half of that.
If your client base is in Los Angeles, for example, you're talking about a 200+ millisecond delay, for every single bit of information that is received. To put it all into perspective, yes, it's only 1/4 second, but over many pages, or large files, it absolutely adds up.