I've got the TubePre and an ART Tube MP or something like that (not to be confused with the ART Digital MPA that I also have and use all the time) - both have not seen a single electron in a couple of years. I simply stopped using the Tube Pre soon after I got it, and I committed a hate-crime on the Tube MP with a 40 watt soldering iron.
Changing the tube in either one didn't improve the sound - the only difference is that replacing a hissy tube with a quiet one would reduce the overall hiss.
Here's what I remember:
Tube Pre:
Pros: you could adjust the amount of tube gain and solid state gain independently -- you could get an OK sound by turning down the tube gain all the way, turning up the solid state gain all the way up, then edging up the tube gain until the overall gain was tolerably high. Too much tube gain and it sounded like ass. Pretty much means it's a low cost solid state pre without much gain.
Cons: Effectively not much gain (see above), but plenty if you don't mind the way the tube sounds. Uses surface mount technology, so it's not really something you can modify if you're inclined to.
Tube MP (which I'm assuming to be somewhat like the unit you mentioned, even though I don't suppose it is)
Pros: does *not* use surface mount technology, and there's lots of information about modding it if you're so inclined. After I changed out the opamps and a few capacitors, it started to sound OK (but not really usable). Then I screwed it up and it blew up.
Cons: sounds horrible - no way to separate the nasty starved plate distortion from the sound.
The TPS II looks like it does allow you to turn down the starved plate sound (assuming it has starved plate tubes), and it looks like it has variable impedance, which is something I really like on my Digital MPA - so I guess it's probably better.