I LOVE ritual spellcasting.
It's a bit clumsier than spellcasting, but well applied can wreck some fantastic havoc.
Even alone, watchers and the health spell circles can do some awesome stuff.
I used the SR NPC Puck in a game I ran in Denver. Gave him an underage magician girlfriend with a focus on health spells. She used rituals to boost up his mental stats to their augmented limit. Which makes him hell on wheels as a technomancer.
Using them effectively as a player requires a bit more finesse and planning, but there are at least two serious arguments for any mage to have it in their toolkit: Watchers (crappy spirits you create to look for things or guard them) and wards (astral walls). Watchers are great for risky situations where you want to check something out in the astral without putting yourself or a more valuable spirit in jeopardy. Wards are delightful because they let you protect a place from astral intrusion and, unlike dual natured ivy/bacteria, they can have a little extras added in. In SR4/3 you could make crossing a ward very dangerous. Those rules aren't in SR5 yet.
As long as you've got someone willing to play spotter, you can wreck quite a bit of hell or gather considerable information via prodigal Spell/Remote Sensing rituals. Lets say your group has two magicians both with magic 6 and a mundane stealth specialist. You want to find a guy you were introduced to last week, whose skipped bail. You have the appropriate lodge and whatnot and an idea where he usually is. So you cast the ritual at force 1 (and use edge to remove the limit). At the beginning of the ritual, your stealth guy heads out to around where you think he might be.
At the end of the hour you finish up and cast Detect [Your "buddy"]. Because you're using a ritual, you get a 1.2km radius (12 total magic performing the ritual *100m * 1 for force) centered on the spotter and, lucky day, you pinpoint him with much more ease than you would have if you tried to track him down on foot. Everyone resists drain, including the mundane spotter, and we all go home with a little extra cash in our pockets and hopefully minimal nose-bleeding.
This also means, if you've got advance warning about where someone is, you can slam them with a high-force combat spell from a mundane. Astral signature could still be a problem, of course, but there are other ways around it.
Basically, it's a specialist's tool.