Reusing Yeast

So, I understand the process of washing yeast, though I've never done it. It seems to me that buying brand new yeast is just not expesive enough to force me into washing old yeast.

That said, I've heard of a lot of people dumping new wort on old yeast. I was hoping to hear from them and find out if they've had any problems. I've put a small amount of new wort on an old yeast cake, swirlled it, and pitched into a clean carboy before and never had a problem. Is this the method most people use? I bring this up because I was chatting with the LHBS guy and he warned me that I should not reuse the yeast from an IPA for a stout as I would pick up to much hop flavor...Not sure I buy that. Any experience input on the subject would be great.

Edit: Safale US-05 Yeast

I think the LHBS guy is wrong. I heard Jamil say he doesn't pay much attention to what type of beer a yeast cake comes from, the impact is marginal if any.

I can see not wanting to go from a super hoppy IPA to some low gravity pale beer, but I would think going into a stout would be pretty harmless.

I've never had a flavor problem using a slury or washed yeast. I've never tried an IPA to a blonde, but could see how in that extreme circumstances it might be a problem.

My LHBS said something similar but it wasn't a flavor thing it was using yeast from a high alcohol content may not leave very viable yeast for the next batch. I see no harm in trying. Go for it and if you have more than 24hrs of no activity pitch a packet of yeast.