But what is really encouraging is that he has been brought in on far lower wages than the existing players.
The guys who were signed when Charles Green and then Craig Mather were chief executives are all on big money.
As has been well documented since, they are earning more than Rangers can afford to pay them.
The Glasgow gants are operating at a loss due, in part, to the rash signing sprees Graham Wallace's predecessors went on.
When Mather was at the helm, for example, he appeared to simply go out and sign whoever Ally McCoist identified as a target.
It seemed like not a thought was given to whether the club could cover their wages. The club is certainly in a mess now as a result of that and other factors.
However, I know for a fact that Darren, who has signed a one-year deal with an option of another year, is not on a huge salary.
He is not going to get the sort of money that he is on anywhere else in Scotland, apart from Celtic.
Nor will he get the profile that he has at Rangers at any other club apart from the Scottish champions.
But he is not on the same sort of cash that the players who joined two years ago or last year are on.
The same is true of Kenny Miller, who signed for the third time last week.
Now Kenny, of course, does not need to worry about his bank balance. He has made his money in a long and highly-successful career.
Still, I am told that the former Scotland international is only the NINTH highest-paid player at Rangers. I think that fact underlines that a new era of financial prudence is now upon us at Ibrox.
These lads are taking home several thousand pounds less than their team-mates.
I have heard some Rangers fans complain about the fact that, at 28, McGregor is not a young player.
A lot of people are uneasy about his fitness because of the serious cruciate ligament injuries that he has had.
But he played nearly 40 games for St Mirren, many of them in the Premiership, last season.
I must have watched him half a dozen times and was always impressed.
He has a bit of pace, he is a good age for a centre-back, he is experienced, he is good in the air and he is very vocal.
McGregor has to learn to cope with the demands of being a Rangers player, but I am sure that he will do so.
His signing also gives Ally options and that is very important.
Ally now has Darren, Lee McCulloch, Seb Faure and Bilel Mohnsi who can all play in the heart of the rearguard.
Luca Gasparotto is still a youngster, but he is a big, strong boy and has featured in the first team before.
But it creates competition for places and gives the manager choices. Who knows? He could play three at the back in future.
He could play McCulloch, McGregor AND Mohsni, and have two full-backs outside them.
Bringing in guys like McGregor and Miller strengthens his squad for what will be a long and demanding campaign against full-time teams in the Championship