I would go for it, there are good reasons to do it (better rewards, dedicated line to call) and no negatives I'm aware of. I feel it's a positive switch. They will expedite the new card to you.
Agreed. There really is no good reason NOT to get the IT card. As an added bonus, one also gets a FICO Transunion score on your IT monthly statement. Granted, that's not a sole reason to get an IT card, but does show the level of customer service available for the IT card vs the More card...where the FICO is not currently available.
That said, it really will not affect your Discover account adversely, or have any impact on your credit reports to change from More to IT. Also, you can get the "standard" IT card colour, or you can go to their card options and order the "garnet" colour card or get a special design card (many like the NYC skyline card - I have that one).