The Blades, who sacked previous boss Danny Wilson with five games of the regular season remaining, are preparing for a third successive year in League One after a second play-off failure.
"It is a very exciting appointment for the club and certainly a positive one moving forward," Maguire told BBC Radio Sheffield.
"It has taken longer than a lot of people were perhaps expecting, but I'm sure it will be worth the wait.
"David has had a fantastic career at the top level, so I look forward to working with him.
"His record speaks for itself and he is also a terrific leader, having captained his country and every club he has played for."
Former Blades defender Chris Morgan took temporary charge of the side following Wilson's departure and will remain at Bramall Lane as coach under Weir.
The 20-year-old added: "I'm delighted to hear Morgs is staying at the club too, because he has played a big part in my development over the last two seasons.
"We've had two seasons in League One now, the first season we were certainly very unfortunate and last term ended in another disappointment.
"I'm sure David will reinvigorate the lads in pre-season though, and come August 3 we'll be raring to go again."