I wouldn't say slowly as such, but all things relative it will always load slower than a fast link in Europe/London because of the jump across the pond.
I'm based in the UK and I'm hosted with Dreamhost and I don't mind the extra fraction of a second it takes to load a page. I don't think your users will notice, unless you've got a very high bandwidth need and therefore it would be wise to move the site to site closer to your customers networks.
Looking at a traceroute from a box based in London/LINX to Dreamhost, you can see the crucial points here:
15 so-1-0-0.mp1.London2.Level3.net (126.96.36.199) 8.080 ms 8.213 ms 8.540 ms
16 unknown.Level3.net (188.8.131.52) 81.296 ms 80.823 ms 80.702 ms
17 so-0-0-0.mp1.LosAngeles1.level3.net (184.108.40.206) 142.547 ms 142.730 ms 142.610 ms
15-16 is the step across the pond and then 16-17 is the step across the US. The last step looks a bit steep at the mometn actually, not sure if there's congestion somewhere.
On average it takes me about 137ms to connect to the Dreamhost box from where I am and I'm on a pretty fast connection. I'm comparing that with speeds of about 17ms to a similar box in London/telehouse.
But I'm yet to see a UK hosting provider match Dreamhost for service and features for the price. Take your pick.