There's a slight Citizens On Patrol vibe to Men At Arms what with Cuddy the Dwarf, Detritus the Troll, and Angua the W... joining the Watch and the reactions of not only the Watch but their own communities to this move. 

Carrot really comes to the fore in Men At Arms what with Vimes impending retirement and it's interesting to see how he steps into lead in his own unique way, what with the majority of the Watch more than happy to shirk responsibility where possible. The Angua and Gaspode angle was decent but felt a little disconnected but the rather sweet relationship formed between Detritus and Cuddy after their initial hostility is very enjoyable. 

It definitely suffers from having to juggle a lot of characters, including many new ones. The first Guards book, Guards Guards, had to carry introducing Vimes, Carrot, Nobby, and Colon and although Men At Arms builds on those characters it also has to introduce Detritus, Cuddy, and Angua to the series while also juggling the main plot of the book and throwing in side characters such as Gaspode, Vetinari, Lady Sybil, and Edward.