The Two Doctors isn't bad, but it isn't spectacular either - and as a follow-up of Holmes after The Caves of Androzani, its pretty underwhelming. Plus, a lot of it is really, really boring. Its incredible, but it is. I like to think that if those three episodes were edited down to 25 minutes, they'd be more entertaining. The 45 minute format hurt the show back then.
Of course, the biggest plus about it was Patrick Troughton as the Second Doctor, who had substantially more to do than he did in The Five Doctors (still not a lot, though). AND, with Frazier Hines as Jamie, no less. The first half of the first episode is really neat.