[Zeke]

Oh, there was a reason given, just a hilariously bad one. Apparently the holodecks run on a power source that's incompatible with the ship's other systems. This is less than convincing when Starfleet can freely interconvert matter and energy; heck, even buying their explanation, they could easily use the holodecks to create something like a motor, then connect it to a generator in Engineering with pulleys or something. That would look funny, but it beats running out of gas, which, as we've seen, leads to ill-fated clones. (Eventually even the writers forgot and we had episodes like "Fair Haven" where holodeck power was transferred someplace else.)

From what I've seen, Tennant is great. Of course, what I've seen is one 90-minute special and he was unconscious for two thirds of it, but he was very convincing as an unconscious guy. (Seriously, I loved him in "The Christmas Invasion," especially the bit with the big button. That summed up the Doctor perfectly -- he's the guy who pushes the big tempting button because he knows more about it than you do and because it's fun to push big tempting buttons.)