It's too early to be making a firm decision on Grimmy's future in the role, but plenty of opinion has been forthcoming on the early signs offered by his debut.
Below, we round up some of the response to Grimshaw's first day from Twitter, Facebook, the papers and our own Digital Spy forum.
Leave your own opinion in our poll and comments box below!
"@TeamMoylesUK Bring back the saviour of Radio 1 #TeamMoyles"
"Nick Grimshaw on the Radio One Breakfast show. I actually turned the radio on this morning!! Progress BBC. Progress."
"Sorry #BBCR1, but I don't see any appeal to Nick Grimshaw. #TeamMoyles"
"Thought I would give it a chance, it got ruined, one direction as record of the week?? Jokes that didn't work then soon after you played Justin bieber? Is this what radio one fans have to look forward to? I am sure the ratings will suffer a massive slide"
"I love @grimmers on breakfast. Every day please! #teamgrimmy"
"Well if Radio 1 wanted to get rid of this 32 year old (which they do), then they've worked. Not for me. Hello Chris (Zoe for this week) on radio 2, already been listening to him for a couple of weeks. Going to miss Moyles and the team...thanks for the last 8 years."
"So listened to #TeamGrimshaw this morning on #Radio1, didn't like the opening, he's generally ok though but not for me, miss#ChrisDJMoyles"
"My fave DJ on the breakfast show ... :). Good times x"
"Grimmy was much better than this when he covered for Mills and was bouncing off Chris and Becky. I think breakfast works better with a zoo format Nick on his own isn't going to work!"
Michael Hogan of The Daily Telegraph
"Overall, this was a promising start – and a clear break from what went before. It was out with dad rock, cynicism and bloatedly self-indulgent banter; in with dance beats, youthful energy and enthusiasm for new music... Ratings might fall but credibility will rise. It's definite progress and I daresay that in a few weeks' time, this show will be even better."
"Go on grimmy! great show dude! @grimmers, love the way the robot calls him "grimey"."
John Plunkett of The Guardian
"Grimshaw's brief is to bring a younger audience to the breakfast show than his 38-year-old predecessor Moyles, who fronted the slot for a record-breaking eight and a half years. It will in all likelihood be a smaller audience, which station controller Ben Cooper won't mind, just so long as it's too much smaller."
"So Nick Grimshaw's first morning show.... Bieber and Styles on the first morning? That tells me all I need to know. #NoThanks"
What did you think of Nick Grimshaw's Radio 1 Breakfast Show debut? Vote in our poll and let us know your thoughts in the comments box below