However, they lost Alexis Sanchez and Olivier Giroud, to United and Chelsea respectively.
Star midfielder Mesut Ozil also committed his future to the club with a new long-term deal and Merson thinks it was a good bit of business by the Gunners.
However, he does believe Arsene Wenger should have signed at least one defender, but nevertheless they should have enough to get past Everton on Saturday (5.30pm).
“In attack, it’s been a really positive window for Arsenal, however, they still need defenders,” Merson told Sky Sports.
“The Bournemouth and the Swansea results will keep cropping up until the end of the season with the defence they have.
“However, I expect them to beat Everton at the Emirates.
“It’s Theo Walcott’s return and he got two goals in midweek but I can’t see anything other than a home win.
“Their home form has been in stark contrast to their away form and you’d expect Pierre-Emerick Aubameyang and Henrikh Mkhitaryan to play.
“If they do I’m expecting a comfortable win for Arsene Wenger and his side.”