I'm glad to see that there are musicians here who are happy to sit in with "better" players and also welcome in "worse" players than themselves. I sometimes drop in at the thread-posting end of TheSession.org to see what outrages have been committed and who's about to assassinate whom. Great fun, but some extreme views on pub sessions from people who care only for their own excellence. To which I've always said, if you hold an open session in a public bar, be prepared to welcome in anyone, whatever their standard, and help them along the way if need be. If you want a centre of excellence, then hire a private room or meet as a clique in your own homes.