It's interesting reading these posts and guessing which posters have kids and which ones don't. As a parent of a 5 year old, one who has been playing with an iPad since he was around 3, I can tell you that managed properly, it's a great advantage for your child to be involved in computers, especially tablets.
The teaching apps for kids are great. My son went into both preschool and kindergarden with a lead on many kids with regards to spelling, math, identification of shapes, colors, vocabulary, etc. And being 'perceived' as 'smart' as early as possible in life is just as important as actually being smart in this competitive world.
My kid is knocking it out of the park at kindergarden; he's popular with his teachers and a large part of that is his comfort with learning and the jump start on learning he received because of our iPad. That can carry over into adult life. People think I'm 'smart' because I'm proficient in Microsoft Excel (macros and pivot tables, people) and can type above 30 WPM.
Getting your child access to a tablet, even if it's a shared family tablet, IMHO, is a no-brainer. When he reaches 1st grade, he's getting a Chromebook (locked down at the router level of course!). Not because I want to spoil him, but because I want him to be competitive in a future world where he'll have to compete for jobs globally.