I'm working on Solus cum Sola (Dowland). I find myself slowing down during the harder parts, and then resuming tempo when the technical challenges relent.
The variations in tempo don't bother me as I listen to myself. But I wonder whether they would be considered bad form by knowledgeable listeners. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html