I'm not all that experienced, but I have yet to get a 'clean' profile from dry yeasts. The only batches I've made that have blown me away were made with Wyeast. I haven't gotten around to doing a side-by-side yet, but every beer I've made with Nottingham has had a distinct, funky, gross-ester-and-dirty-fermentation taste. I'm learning more every day about proper aeration, pitching rates, fermentation temps, etc, but even a recent APA I made with Nottingham for a friend* has this foul yeast profile. Clean isn't everything - most styles benefit from good yeast characters - but I'd have preferred that to what I got.
Anyone tried Cooper's, by the way? Haven't tried it since my first batch. Nothing good to say about that, either.
*Friends shouldn't let friends use this yeast.