386 vs 686 kernels

[Dazed_75]

I do understand what the basic difference is between the 386 and 686
versions of the kernel and would expect that the 686 kernel would be
an advantage with my P4 3 Ghz machine (actually for any machine with a
newer than 386 processor).  My question though is twofold:

1) Is there any drawback to upgrading my Ubuntu 5.10 (or 6,x soon) to
using a 686 version of the kernel?

2) Is there any good reason for a package manager like Synaptic NOT to
recognize and suggest the possible upgrade?

-- 

Nothing is really work unless you would rather be doing something else.
  - James M. Barrie