After tweaking the amp a little more, and with the Tone Tubby ceramic San Rafael 10" speaker installed, here are my impressions of how the Tramp sounds.
In Tweed mode it goes from cleans to a nice breakup, similar to a Tweed Champ or Princeton. To do the Tweed thing you would normally turn the MV all the way up, since Tweed amps don't have an MV, and then adjust playing volume with the Volume/Gain control. The overall tone is a little dark (or "woolly"), exactly as you would expect with a Tweed. Perfect for some smoky blues. I also found myself going for the Neil Young chords, as not surprisingly it nails his tweed tones. Les Paul players may prefer to use the front-panel fat/thin switch on the thin setting, and the Treble and Bass controls also come in very useful here. i really like the San Rafael speaker's nice balanced tone.
In 'tude mode, the amp engages a higher gain range, with a brighter edge on the tone. Rolling the Volume/Gain control back still yields some great chimey cleans. Gradually increasing the Volume/Gain control takes the it past a gentle breakup and into Marshall territory, and even some way further towards Mesa land. With all of the controls dimed (including the tone pots) it's total filth, with the San Rafael also contributing to the breakup.

You can also dial down the MV control without losing tone. You can get nice bedroom playing levels by using the MV and Power Control (VVR) together. The VVR can yield some nice brown tones as well, when its turned down.
This is still a work in progress, but I sense we're getting close now. So now it's a matter of getting feedback from more different players. Stephen tells me that Lawrence tried it yesterday, and preferred the brighter Jensen alnico speaker. So we have some differences in taste here, which is a good thing.
