I bought a Maroc Telecom prepaid SIM and I've been happy with it.
I haven't found any sort of English menus or voice prompts though, french and arabic only. The guy at the teleboutique or maroc telecom shop can do the initial setup of APN and whatnot for you.
Note that there are separate credit balances for voice vs data so when you add credit to the phone you need to specify if you want it to go towards data (internet access) or else it will go to voice.

Accueil - Portail Maroc Telecom - Portail Maroc Telecom

To add credit to your phone buy a Maroc Telecom scratch card from any teleboutique. You can add credit to the phone by voice or by SMS.

Voice:
Call 555 then selection menu option 1 then enter the code from the back of the recharge card. Put "*3" at the end of the code if you want the credit to go to your internet access.

SMS:
Send an SMS to 555 with the code from the back of the recharge card.
Put "*3" at the end of the code if you want the credit to go to your internet access.

You should almost instantly get an SMS confirmation about the transaction and new balance.

You can check your balance (voice and data) by calling 580. Hope you understand french or arabic. Sometimes it has worked for me to send a blank or single character sms to 580 and I will get an SMS response with the balance. Doesn't always work though.

A 10 dirham recharge will get you 1 day of internet access. 50 dirham recharge will get you 10 days.

Coverage is pretty good.

On my phone the vendor had for some reason set "network mode" to WCDMA only and I found that sometimes there was no service in places where other people had connection. So I reset it to "GSM/WCDMA (Auto)" and it was better.

I've noticed wifi access to become more common and have found open access points at several restaurants and Ziz gas stations.

__________________
Wrong way to Kathmandu - A Sidecar Misadventure